Pardinuz: Could be interesting if executed well.
Though, on the surface it sounds like it would be a hell of a grind.
Also I agree with Gnostic, that kind of grind was bearable in a platformer like Rogue Legacy where it takes a split second to defeat an enemy. In a game like this it could easily become very repetitive.
Here's one thing about roguelikes that is different from typical turn-based RPGs; combat (in cases when you don't need to think) is much faster. In traditional ASCII roguelikes, for example, all you need to do is walk into an enemy and you automatically attack it. In Mystery Dungeon games, attacking is just a matter of pressing a button to attack, just like in a typical action game.
As a result, if you are massively overleveled relative to your enemies, you can kill them quickly; each enemy takes only a split second. Things only slow down when you actually have to think. (Of course, in some roguelikes, you may need to be careful about rushing too quickly, especially if an otherwise weak enemy can do nasty things to you.)
(As a side note, it is possible for an SRPG to do combat like this. The Disgaea series does not, but the Arc the Lad series, for example, does, as do the Gold Box games; in the former, attacking is just pressing a button, and in the latter, running into an enemy makes you attack.)