I will probably be stoned to death for what I will say in this post but I haven't heard this opinion anywhere and I want to put it up here with the risk of becoming the most wanted Tenno.
Trinity and Rhino are one of the most problematic frames in the game and their design hurts the game.
First, our beloved Trinity. If I were to make a tier list Trinity would be S++++ because she trivializes the entire game. A support that makes the entire team unkillable and offers and endless supply of energy, both actions done with the press of two different buttons, it's not good in my book. People have been asking for a challenge in the game, well you can't have challange in a game where one character just keeps the only 2 resources the game wants you to manage maxed. She makes nuke frames beyond overpowered because they don't have to manage energy and positioning and movement are stuff you can forget about when Trinity anyway heals you to max with one button. The only workaround DE has found is the ability negating mechanics which everyone hates as they only make things annoying if not anything else. Not to mention, other support frames fall flat in the face of Trinity because none can offer what she offers, the only one close to Trin's level of support is Harrow but Harrow actually needs some skill to play effectively and actually help the team. It's not rocket science but it's more than just pressing one button.
With this said, Trinity needs a rework. I'm fine having a general purpose support that has as main perk replenishing allies resources but this must be done in a different way. Healing an entire team to full HP and shields must be something hard to pull of and keeping everyone's energy maxed must again be something difficult to do. I don't have any ideas for this said rework, but I know it's a must if there's any chance of having challenging content in Warframe, ever. Anything they pump out will always be made easy by having a Trinity in the squad.
Now, onto Rhino. I honestly don't have that much of an issue with Rhino. Sure, he suffers from the same one button win syndrome but at least his one button just buffs the damage of everyone which isn't so bad. His iron skin could be made to function like Nezha's shield in my opinion since just straight out invulnerability to X amount of damage isn't ok at all. My biggest problem with Rhino is how he is obtained. For most new players, he is the second warframe after the starter and this is a huge issue. In the hands of a completely new player you give a frame that cannot die and has one of the best buffs in the game. Guess what this leads to? That new player skyrocketing through the rest of the starchart because they can't die due to iron skin, while also having a window to most high level content. Some strength, some duration and all new players are ready to go into pretty much anything with a buff Rhino build. So in short, my issue is that the game gives such a powerful frame like Rhino too early and too lightly. I don't think Rhino needs any substatial nerfs besides the iron skin change I mentioned but I do believe he should be put further into the game. There's absolutely no logic in giving a new player an unkillable frame that also happens to be one of the best buffers with little effort from the get go.
With that said, I don't think Trinity and Rhino are the only problems Warframe have and that fixing them will fix the whole game. But I do consider they are part of the bigger problem and it would be best for everyone if DE would look at them. Sometimes it's not only weak frames that need a rework.
I'm perfectly aware I just stirred the entire masses of Trinity and Rhino loyalists so feel free to call me a mental retard if you feel like that's what I am. Most probably this won't get anywhere but I will feel better having my opinion out there.
P.S I know trinity got nerfed before but honestly it didn't achieve anything.