This video/article perfectly explains why vertical progression has so many problems. Why players are frustrated with the way difficulty scales, the immense amounts of grinding (essentially playing content that isn't fun in order to gain access to content that is). The guy in the video/article explains it better than I can in my own words so just watch/read it.
http://taugrim.com/2012/04/19/why-games-should-scale-horizontally-instead-of-vertically/
The guy in the video explains the problems that arise from using vertical progression in an MMO and how horizontal progression could be used to solve those problems. I'm going to talk about games that already utilize horizontal progression, why it's effective, and how it could be applied to Warframe.
Deus Ex: Human Revolution (yes, I know it's not an MMO, bare with me).
As you progress through Deus Ex, you accumulate XP and money. Money can be used to buy various consumables and weapons while XP is converted into praxis points which are spent on upgrades.
Here's the key with Deus Ex, you can beat the entire game without spending a single praxis point or buying anything; the upgrades simply give you more ways of playing the game. Invisibility, radar, and hacking allow a more stealthy style while improving accuracy on the move and and maximum energy lends to a run and gun play-style.
The reason why this makes Deus Ex so much fun is because starting the game each time is a fresh experience. Playing through once using non lethal weapons and stealth is a completely different experience than bombing and machine-gunning your way through an army of Chinese gang members, it's almost a whole knew game. You also don't feel obligated to get certain upgrades or do certain missions for practical reasons. In Warframe, stacking as many damage mods as possible is objectively the most effective way to play. In Deus Ex, you can't do this because there are no damage mods, upgrades either give you new ways of dealing damage or allow you to complete missions in ways other than dealing damage.
Obviously, a character with upgrades is objectively better than a character with no upgrades, the point of implementing horizontal progression isn't to make every player the same strength regardless of their play time and number of upgrades acquired. The point is to; A) make all content relevant to all players, B) minimize power creep and min/maxing, and C) make progression fun rather than grindy by encouraging players to pursue their preferred play-style to complete content instead of grinding for a higher tier weapon.
Actually, I think I'm going to stop here, I don't need to list more games with horizontal progression, it'll just be redundant, NEXT!
Possible Objections:
"but people won't play as long or as often without the lure of better gear to drive them."
I have two responses to this: If you're motivating factor for playing a game is the compulsion to get better gear then you should reconsider why you're playing that game *cough* Skyrim *cough*. My second response is this, games such as Super Smash bros, Starcraft, and League of legends lack this compulsion yet millions of player, including myself have spent upwards of a thousand hours playing them. I know that the PvP is what drives people to play these games and it is therefore, dis-analogous to compare them, my point is that having fun core gameplay will retain players more than any amount of shiny loot.
"Games can have horizontal progression within tiers."
Yes they can, and most games with vertical progression, including Warframe, do. The reason why I'm advocating the removal of vertical progression is that it causes most of the content to be irrelevant at any given time. There's no reason to play Mercury or any other low level planets if you have end game gear, even if you're leveling it, and alerts are a poor band-aid fix for that. This extends to weapons too, there are a few weapons that are simply better than everything else. If somebody likes the feel of the Karak or Furis than they should be able to use them all game. You might respond to that by saying "Prime and wraith variants of outclassed weapons solve that problem." This is true, but it also requires DE to make tons of content that will only be experienced briefly, if at all. I'm sure game developers want to get as much use out of all their work as possible and horizontal progression helps achieve that.
