I should probably say that my angle for "epic" is mostly for when heroes meet epic NPCs. I want a rough outline of what a true Archmage can do, and things like ignoring the general rules on concentration, attunement and spellcasting seems appropriate.
A secondary concern is for play at the earliest epic levels.
What I'm not bothered too much about, is play at level 30 or thereabouts. At this stage, yes proficiency bonuses are off the scale. But so is everything else. There are no monsters above CR 30, and we can't expect heroes to just fight increasing numbers of Tiamat cousins.
That's why I feel the proficiency concern is slightly off target. And many of the boon concerns too. At levels 20, 21, 22 or so the skil bonuses aren't meaningfully different from at level 19.
What held true at the regular levels still do. The only difference is that some characters will have their capstone (most will probably have multiclassed a long time ago), and they will have an Epic Boon each (or perhaps two at the most).
There's nothing there which breaks the game, unless it's already broken in your opinion (which is fair). Sure a couple of the boons are powerful, but we're talking about level 20ish characters.
Yes, the ability to keep pushing your prime stat up to 30 will eventually destroy the game. Or at least destroy it even more than it's already destroyed. But my main focus isn't at the end, when every boon is in play, and everything is "filled in".
I'm mostly interested in feedback on the impact of your first boon when you become epic at level 20 or 21 or so.
Specifically, I am really interested in juxtapositing some of the raw boons with my replacements.
For instance, the Boon of Combat Prowess. Sure, automatically hitting with your first attack of the round is great.
But is it really FUBAR? Attacking is what you
do. You don't need a completely new power. Everything the boon does for you, you already know how to do. All it does is give you some reliability.
Compare to the original boon, which gives you one auto-hit per rest. Come on, that's
nothing.
I am willing to discuss whether my version is overpowered, but first I'm interested in your opinion on the original boons I've changed.
Consider my boons a conversation starter.

I want to show how far off the mark I find some of the original boons, by showing an alternative.