The Tavern

Why?

Heal-on-kill with no other healing heavily encourages saving weak monsters for later: If you run away from a fight at very low HP, then finding and killing new monsters will be very dangerous, but killing a stashed weak monster is a guaranteed and highly annoying way of healing. (If heal-on-kill depends on the power of the monster, the player can still stash a strong not fast meele-only foe.)

A new idea: 1) no healing whatsoever possible 2) a lot of hit points 3) an activated ability: invulnerability for a few turns (take no damage) with a breath timer.

This kills you way too long after you make your mistakes though - I don't like it. I guess it's already in the game to a degree if you actually die by a million cuts and run out of wand charges/mp, but it seems much worse when that's effectively the only way to die.

I would just make it so only consumable sources of healing work at all. Scrolls of recharging are plentiful, and maybe their ability would get some use this way.

Elv and Trog have appeal beyond healing. Mahk could give MP instead

This actually opens up more gods, instead if having a handful of "optimal" ones

You still have the slow heal plus damage shaving combo, which I think sticks as close as possible to what was originally intended with deep dwarves.