I think he's worse than Lotleth Troll
, which I'd be much more concerned about r.e. regeneration. Troll sucks. Varolz, by contrast, is at least allowing your opponent to trade their attacker for your worst creature. Sure, it's free, but eventually you'll run out of creatures to sacrifice to him.
But, on the other hand, why risk it? selfmill and sacrificey stuff are literally BG's most common draft themes. Skyfisher Spider
is one example of a BG card that does those things and is also powerful in a way that won't go sour as easily. I could also see Izoni or Charnel Troll or even Uurg fulfilling similar roles.