Let me start by saying this: Certain frames and weapons absolutely need a nerf that goes without saying. Whinge and cry all you like but if you can't tell when something is OP then you really shouldn't be allowed to weigh in on this subject. That being said this is my personal belief:
Balancing Warframe only requires a more intelligent approach, once that appropriately would require a lot of hard work, but in the end I feel would be worth it *if* it could be accomplished. Don't get me wrong, power creep can be dangerous, but handled appropriately I feel like we can accomplish harder (I.E. more fun) game play without needing to excessively buff enemies or nerf Frames/weapons. The real ticket here is allowing the enemies to intelligently use the means already at their disposal more effectively. At the moment the game consists of many enemies that are little more than road bumps, taking certain ones out might force you to slow down a bit, but in the end it's just a hiccup on your way to the end of the mission. Or worse, you simply ignore them because your objective is to reach the end of the map (I'm looking at you capture and rescue missions).
Now before I start running my mouth about changes, lets take a moment to recognize how many people would be upset that they couldn't simply fly through a capture/rescue mission for their void traces anymore. Now promptly ignore those people, they do not want the game to be 'better' they want their dopamine fix when they break open a relic or sell some random garbage on the market for plat. These kinds of people, while they do serve a purpose, will always settle into 'what's easiest'. Once the dust settles they'll find the most min-maxed/meta way of doing things in this brave new world, so ignore any complaints they have.
I fully understand that rescue missions are the way they are because some people hate escort missions, AI can get stuck preventing completion of missions, and the default Warframe experience is 'gotta go fast'. But I would much rather see a proper unit that has to actually make its way to the extraction, no teleporting, possibly with parts of the mission being defense-like where they lock down a door that leads towards extraction forcing you to defend the target while someone runs to some console somewhere to open the door. It would also give certain frames a more meta role in rescue like Nova and Loki to move the rescue target over long distances or Volt to make them faster.
Similarly capture missions should be much more involved, a capture target shouldn't just be walking out in the open two maps over. They should be guarded, maybe in a secure location. Imagine a mission that is more Spy-like with multiple potential locations to check to find the capture target, if you can get in silently like a spy mission then you can possibly one shot them and get in and out quickly. But if you set off the alarms on the way to them then they're swarmed with defenses, or possibly start bee-lining for an exit like they do now but with a group of enemies to defend them on the way.
That being said I'd like to take a look at a little something we've all looked over, that being the stats page at the end of a mission. It could be an interesting factor in helping to create a bit more balance. We've all played the 'whose better' game, where you glance at the stats occasionally, see someone has a slightly higher damage % than you and decide 'Oh looks like I need to kick it up a notch'. It can be a fun little game to play on the side while you're mindlessly wiping enemies off the map. But what if those stats had a hand in determining just how hard things are for you? For example:
Is one player doing the majority % of damage? Have most enemies focus on them, sending specialized units after them, bombard them with orbital strikes on outdoors maps, toss nullifier grenades at them to disrupt their abilities. Hell maybe give Energy Leech/Parasitic eximus a special grenade or move to drain the entirety of a warframes energy in one move if hit. If a nuke frame is killing most enemies then it should be their primary target, it's just common sense.
Majority of enemies being CCed? Activate some kind of experimental power damper that suppresses Warframe abilities for a minute or two then burns itself out or have enemies intelligently group up in nullifier bubbles, perhaps even allow bubbles to merge and become more powerful so that multiple nullifiers together make larger bubbles. Different eximus units could change how the nullifier field works, an arctic eximus inside one could reinforce it to not shrink when shot and be stronger like the snow globe barrier they normally have, Arson eximus could expand the bubble with their blast, negating abilities in the blast range but 'popping' the bubble forcing it to regen as if it were taken away by gunfire, and so on. Nullifiers should also be reworked to not do things like popping Limbo's bubble, only allowing enemies in the bubble to pass through it. With a change like this you could have an enemy in a nullifier orb walk into limbo's rift. Toss a small nullifier grenade at the objective (effectively putting the objective back into real space) and presto, now all the enemies outside the Limbo bubble can shoot the objective again. Of course, this would require enemies that were smart enough not to walk into a Limbo bubble in the first place.
Now of course, enemies getting around CC would mostly involve nullifiers, but I feel like an argument could be made for certain enemy types having an innate resistance to Warframe abilities, such as decreased duration on Warframe abilities, or reduced damage from abilities. It just makes sense that a Nox should be better at breaking its way out of Khora's chains or shaking off Volt's stun a bit faster than your average grunt, and it would change normal CC from 'stop everything and kill it' to 'stop the small frys so we can focus on the big problems'.
Harder enemies need to be more common, in more ways than one. For one, why are all the really difficult corpus enemies only in Orb Vallis? I've been knocked for a loop occasionally on some of the harder Vallis missions but meanwhile their ships and stations only have basic grunts and the occasional nullifier. In the same vein, I know certain enemy types exist, and yet almost never see them unless I stay in a mission for thirty minutes. More intelligent use of enemy types should go without saying, as well as improving on their anti-warframe strategies. Obviously on the Corpus side most of their strategies would revolve around nullifying abilities and then taking the frame out while it can't defend itself, and yet they have no means to actually get you into the nullifier bubble other than just walking up to you. It seems that a unit much like the grineer scorpion would be ideal to drag you in to it, yet they have nothing of the kind, similarly grineer commanders would be perfect for teleporting you next to a nullifier which could then activate while you were stunned stripping you of your protections. Perhaps if they ever decided to join forces against the tenno we could see some of these strategies put to work.
Personally I'd love to see more combo attacks in general, like commanders teaming up with Drahk Masters. Have a unit disarm the warframe, then teleport him across the map so they can't quickly get their weapon back (Frankly it'd be hilarious if other units could pick your weapon up and use it against you/other allies, obviously killing them would drop it so you could re-aquire it). Then bumrush the Warframe with scorpions, noxes, eximus, whatever. Aside from tactics, one of the main things that needs to change is the whole 'mindlessly running into combat' The majority of units have guns, do they really need to be three feet from the objective/enemy? Hydron/Helene isn't the best example because it has pillars blocking all four cardinal directions up top and has to be gotten close to when it's lowered, but there are plenty of defense maps where the objective can be seen from (and fired at) from very far away. A Fastva build shouldn't even be an effective means of grouping enemies because they shouldn't be stupid enough to group up at a defense objective in the first place.
I'd love to see more weaponry that was effective at battling warframes, like Nox's stug slowing you down to make you easier to hit, perhaps even inhibiting double jumping/bullet jumping while you're affected. For example, their Stug attack could stack up to three times, increasing the duration of the effect with each stack. The first stack could slow you as it does now, the second could prevent double jumping, and the third prevent bullet jumping until the duration expires. Making Nox a much more effective unit at forcing a Warframe into a battle they may not want to fight.
The other issue is enemy levels, I understand the need for a game to have increasing difficulty over time, but I would much rather see a more fluid and reactive increase in difficulty that was determined on player skill levels rather than +5 level per round or whatever. If the enemy can't even touch the defense target in the first few rounds, then maybe there should be a much more drastic spike in enemy level for the next few. Or, let's say we have a group of four on Hydron, an MR28 Saryn Prime, an MR6 Excalibur, and two Mid-teen MR people playing whatever. Using my above guidelines the MR6 is obviously doing like 4% of the total damage, so the grineer are going to mostly ignore them. The Saryn doing 70% of the total damage on the other hand is a major target, now imagine among all the level 40-50 enemies suddenly a level 100 scorpion and Nox are sent out targeting the Saryn, they'll attack whatever attacks them, but will prioritize heading straight for the MR28 player. Now sure, they may one shot the unsuspecting Excalibur on the path to Saryn, but that's what teammates are for anyway. As long as their AI is good enough to move on once the Excalibur goes down and not stick around griefing him then I see no issues with the occasional death squad sent out to deal with the big fish in the pond. Even without the added trouble of programming in all the 'targeting a specific player' stuff I feel like having the occasional high level enemy mixed in with the other enemies would be more fun.
A bit rambling, but I think I got the point across. More in depth game modes and more adaptive AI/enemy levels for a deeper and more satisfying game experience. Obviously I would rather see AI that can more intelligently work around OP abilities rather than having those abilities nerfed, but I also understand that programming AI to respond to a hundred different scenarios that various abilities can present wouldn't be easy. And yes I'm fully aware that more nullifiers doesn't equal more fun for most people, I'm mostly advocating for smarter usage of the technology, not necessarily more of the unit in question.
Keep in mind, these are just some random thoughts I had, I feel no need to defend my opinions or ideas. If you want to discuss amongst yourselves feel free, if you want to nitpick at me don't bother I rarely return to the scene of my crimes (posts). I just felt like getting some random ideas out of my head after reading the Pablo thread, it seems premature to say improved AI alone wouldn't be enough for real difficulty. Certainly improved AI doesn't count for much if you can wipe everything out in an instant, but that's why enemies have levels. With intelligent use of the systems already in place and (much) smarter AI I feel like minimal nerfs would be necessary (I'm looking at you Saryn). Sure I'd be a little pissed if my Vortex got cancelled because some smarmy corpus unit threw a nullifier grenade into it, but I'd also be kinda proud of the bastard right before I wiped him off the face of the planet, or moon, or space station, whatever you get the idea.