At least as of late, Blizzard's class balancing philosophy seems to be that they want to make sure people are using each of their talent trees - which is perfectly valid, but the implementation is a bit misguided. More specifically, the goal doesn't seem to be that each class would have at least one good PvP or PvE spec... but that you have some subset of each class specced deep into all of their trees, no matter what the overall picture looks like.
I think it's a difference in interest between hybrid and the more specialized classes, actually.
Rogues (and Warlocks, Mages, Warriors, Hunters) don't really care if there's more than one viable tree. Having all three trees viable in PvP or PvE would be nice, but the bigger concern is that there is at least _something_ you can spec to and do well in either PvP or PvE. Respeccing for serious PvP (or PvE) is a fact of life and it's something most people are okay with. It'd be nice if every tree was equally special and strong, but they're not, and we're okay with that. The bigger concern is that there's an option for both PvP and PvE that doesn't make us feel like we're trying to tear down a wall with a paper clip.
Hybrids (Paladins, Priests, Druids, Shamans) are much more concerned with this. As a general rule, even if you have to respec what's a decent set of PvE gear for your class is a decent set of starting PvP gear. Damage is damage, after all, and you use stuff you get in PvE to offset your PvP gear until you get enough honor/arena points to replace them. You have to respec; you don't have to regear. An Enhancement Shaman or Retadin probably doesn't _have_ backup Elemental or Holy gear to switch to when they want to go PvP; they can either go as a bad spec, or with terrible gear. Obviously once they get enough PvP gear it may not matter, but starting out is incredibly rough.
Hence... the hybrid classes want their hybrid specs to be PvP viable as well, and the more specialized classes who can cross-pollinate gear even if they do have to respec every week look at them like they're nuts. "What do you care if Ret is good? Holy is amazing in Arenas!" Except the Retadin doesn't have the gear to _go_ Holy... and thus, the breakdown in communication.
Conversely, Rogues would rather have one PvP spec that just _works_ rather than three viable specs, which is why this is so frusturating. They're applying the hybrid design balancing to specialized classes that don't need it.