Also in this game firebolt deaks 1d6 fire damage, not 1d10 like in D&D5e rules.
I'm 99% sure that's because of burn.
It absolutely is. The burn makes it wayyyy stronger generally than a flat 1d10 would.
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I'd love more short rests between long rests, but only if long rests were more restricted somehow. Not sure how to balance long rests, though, given that both tying it to an in game time system or out of game time would be awkward.
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Until I got to the Underdark a single short rest felt ok, but now is not nearly enough. Even at level 4 every encounter takes a lot, and the map itself is like a minefield.
I think the Underdark is pretty heavily balanced around a level 5 party. It's certainly Doable currently, but sometimes you just get one turned TPK'd
