It's more the userbase of the Smogon server made those pokemon NU. The tier-list just changed to fit the statistics. --- Si || I'm a Saint, a Sinner, a Siren of the word. Showdown at midnight. http://i41.tinypic.com/121sc60.jpg
great now I have to load up my bellyzard and sweep a few teams for old time sakes. All kidding aside though, did SR become THAT prevalent? And what's with the Electivire hate? And to a lesser extent, the Porygon-Z hate? They (sorta) pwn.
Stealth rock is used on 90% of all temas these days, making charizard, and even people like Yanma not worth using. In addition to that, he isn't breaking the UU tier, so no need for him to be BL, as BL is really just the "Uber" of UU.
PorygonZ was tested in UU, but found to be broken, so moved up to BL.
Not sure when regigigas was considered even remotely useful competitively though. --- Our divided brothers we slay