In my current playthrough, I've been puzzled by not being able to revive any dead characters. I get the crown options, but once I click on revivify or raise dead, both options turn gray and nothing happens. I just realized this is probably because my barbarian is wearing the crown, and at the end of combat she still has active rage, which prevents spellcasting.
What's even more funny is that I chose druid over cleric because of the latest DLC adding druids. But wait, he is unable to cast any of those numerous scrolls of revivify or raise dead that I've collected because those spells are not in the druid spell list.
In short, I've had no option to prevent game over if anyone dies during combat. Technically this is not a bug, but only because the game immediately checks for revivify/raise dead at the end of combat. Logically, I should be able to drop the rage and use the crown.
In any case, I have to take this into consideration in future playthroughs or until the issue is resolved by automatically dropping rage at the end of combat, before checking for crown options.