I'm fine with having access to the more powerful abilities early on. The player really shouldn't be struggling at the beginning of the game while they're still trying to work out how to play the game. If someone figures out how to one-shot enemies in their first few fights, I don't see a problem with that. It's when they keep one-shotting enemies (multiple enemies at once, even) all the way through to the final fight that it's a problem.
If you give the player all the best tools in the game this early, of course he's gonna break balance and it also ruins the sense of character progression later on.
If your character is done at level 7 for all intents and purposes, then the only thing mattering after that is some armor and weapon changes later on all the way to level 20+. At this point the next level is just some number increases and some fluff to the build
Every level up should feel important and a character shouldn't feel "done" for as long as possible. There should be something to make players go "ooooh, shiny" at the end when they reach those later levels. Stuff with actual meat to them that feels like it matters
Which swings me back around to the point that i feel like that warriors being OP isn't a problem per se, as it's inevitable in these games and expected for end game, but that the synergy of 'best tools' and completing a warrior build is made to easy to finish early
