I think an MR hero is a great idea when your meta includes lots of spells that allow it - Big Waaagh! and Death are the worst offenders here. No one wants foot trashing their bunker until it runs off the board, and no one wants Death sniping their characters off from across the board either (note that Big Waaagh! can do this to a degree too). I'm probably forgetting some lores here too but those are the ones I can think of right off the bat.
If the meta is heavy that way, I'd say put it on a cheap character. The other issue is - if you are playing vamps, I don't know how cheap your cheapest character is. For skaven, it's 15 points for that engineer. For Orcs it's 30 for the Night Goblin Big Boss. But for Chaos, it's 110 for that exalted champion - probably not worth it there. Even with elven heroes coming in at 70ish points - that's still pretty hefty for a 4/5 up ward against a very limited spell selection.