I think one problem with casters vs. non-casters is what I call "blah levels" (I don't like the term dead levels, but if you prefer, use that instead). You go up a level and...not much happens of note other than hit points increasing.
Now, ever since, I don't know, the dawn of time, full casters get new spell levels to access every odd level (until, weirdly 19th). So no matter what happens, every off level you get a new plateau of power.
Now let's look at the Fighter. It sure looks like he gets something cool at every level, doesn't he? (or she, or it, not being genderist here).
But let's take a deeper look. Well at level 3, he's just getting his subclass abilities. Some casters already had theirs, and they're getting 2nd level spells.
Level 4, he gets nothing nobody else gets. Skip.
Level 5, he gets extra attack. Full casters get 3rd level spells. Ok.
Level 6, hey, I got an ASI! Woot!
Level 7, hit the subclass train again...of course, the Wizard got his last level and now he gets 4th level spells...
Level 8, ASI for all. Skip.
Level 9, uh...once per day reroll on a save vs. 5th level spells? Hold on...
Level 10, subclass train! Oh for the Wizard too.
Level 11, yeah baby, Extra Attack x 2! And 6th level spells.
Level 12, ASI for all. Skip.
Level 13, Indomitable x 2 vs. 7th level spells. You have GOT to be kidding me.
Level 14, bonus ASI! Wizard gets subclass feature.
Level 15, subclass train, whoo whoo! 8th level spells.
Level 16, ASI for all. Skip.
Level 17, Action Surge x 2, now that's sweet! Indomitable x 3...ehh... Meanwhile, 9th level spells. Doesn't seem equal to me. You can Wish the whole party has resistance to a damage type, I get an extra action per short rest and a reroll.
Level 18, Subclass Train. Wizard gets two low levels spells he can spam like cantrips!
Level 19, ASI's for all. No new spells for you, Wizzo!
Level 20, Extra Attack x 3 is sweet! And all the Wizard gets is 2 bonus 3rd level spells per day? Finally, got one over on him! Oh wait...the game is over now?
At the very least, odd numbered levels are exciting for full castes AND they get other toys.
Non-casters get far fewer exciting levels. Even without taking relative power into account, why is that? And is there any excuse for Indomitable being so terrible?
You might say "well, rerolling a failed save can be amazing!" and I'm like, I guess so? Of course, when Wizards wants to write things like Silvery Barbs, how amazing is that again? Plus, let's not forget, that without supernatural assistance, Fighters only have, at best, 3 decent saves anyways. Rerolling a save that only succeeds on an 18-20 isn't great. The Fighter should be receiving bonus Resilient at these levels, not a darned reroll!
