Should the player be able to die?

There is never a tactical benefit to death (that is, when you don't have death protection) so nobody would willingly click on an enemy with a big red DEATH combat prediction. Even if your character is stuck and must kill themself to end the dungeon run, there's a surrender option in the main menu.
With this in mind, the fact that dying on an enemy is possible, let alone possible without any sort of 'Are you sure? This enemy will kill you.' is rather odd. You can already lose by messing something up and being forced to retire (or surrender) so all being able to die adds to the game is that the player sometimes experiences a glitch or misclick that removes any progress they made on the current dungeon run and 50 gold (more of an insult than any amount of real money, to be sure) for whatever item they brought in.
With this in mind, the fact that dying on an enemy is possible, let alone possible without any sort of 'Are you sure? This enemy will kill you.' is rather odd. You can already lose by messing something up and being forced to retire (or surrender) so all being able to die adds to the game is that the player sometimes experiences a glitch or misclick that removes any progress they made on the current dungeon run and 50 gold (more of an insult than any amount of real money, to be sure) for whatever item they brought in.