Chaosmancer
Legend
I think the framing of kill here is incorrect. I am around a lot of new DMs, and their frustration comes from not being able to challenge the PCs without the threat of having a TPK. If framed that way, then these new class powers will indeed frustrate some DMs, even experienced ones.
The old rule of - wait and see - should be our go to here. As we really haven't seen the MM yet. But, for pure speculation's sake, the new class abilities might frustrate DMs.
On a separate, yet similar topic, the new classes definitely seem like they will slow combat a lot.
But is that because the game made the PCs too powerful to challenge unless you are going to TPK them... or is it because they are new DMs and it is hard to find the right balance? Because I note, you don't say that their frustration comes from not being able to challenge the PCs, but that they can't challenge the PCs without risking a TPK.
In that vein, making a TPK HARDER to achieve will mean that the new DM is more likely to be able to challenge them without TPKing the party. Which removes the frustration.