I think this is an interesting card. It works nicely with the various death effect cards like bonewall, soulcatcher, condor, boneyard. (yes, I know skeletons can't be sacrificed to it, but they help mitigate the cost in the first place) The mechanic, while ostensibly a drawback, can be used to advantage in several situations. It would work nicely with things like shard of patience, all the death cards I mentioned already, and it would be good against things like shard of sacrifice, and somewhat resistant to things like sundial or certain shields. (fireshield, dimshield, etc; you can just wait them out)
Two quick points, though:
1) Singularity. Pretty sure that's not a 'worthy creature' either :p
2) What happens if you play adrenaline on this? Would it attack once and stop, or attack multiple times, or attack multiple times if you sacrifice multiple creatures?