My DM is using this homebrew version of True Strike - too powerful?

[Zhorn]

I'd steer clear of the expanded crit range proposal for the same reason as the guaranteed crit one, cantrips are too easily tacked onto builds that get more mileage out of crits than others (rogues, paladins, hexblades) that it'll really up the damage disparity with more reliable nova-potentials.

Either go for the Auto hit: singular, no crit chance, but lands a reliable hit
Or the scaling 1d4 +To Hit per-tier modifier

Also avoid any proposals for the cantrip granting advantage, that's one of the pitfalls that made True Strike a nightmare to balance in the first place.
And tacking on extra damage on top of that again is just power creep.