Just to point out, despite not playing UU much, revenge killing is not a viable argument for a pokemon being Uber for it's metagame.
Salamance is easily revenged by Scizor, or anything with Ice Shard [Weavile especially]
Latias was easily revenged by Tyranitar, and often by Scizor as well.
Porygon-Z was easy to revenge kill as well, using a UU example.
All of these pokemon became Uber for their respective teirs. Revenge killing =/= countering. A pokemon fits a clause if it has few to no counters.
And, from the posts I'm reading, if Heracross is usually getting 2 kills in a metagame braced for it, that bodes well for Heracross remaining in UU. Imagine how much damage Heracross would do once UU settles, and teams are not overprepareing for Heracross.
Eh, I might drop into UU for a while to see the devastation for myself. And take a break from NU.