...........Shammy healers were remarkably underpowered compared to the other healers for 99% of the situations in game. The other healers weren't going to get buffed to make them viable for PvP because they were already strong enough in PvE, and Shammies weren't going to get buffed for PvE because they were already the best PvP healers.
That is the whole problem right there, and it will never go away. Even if PvP ever does achieve something close to blanced, the players will always scream "IMBA - fitz da PvP" And their suggestion is nearly always, "Buff my class". Lot of PvPer's don't want to play balanced PvP, they want to be able to ROFLstomp everyone who has not yet discovered their "perfect PvP build".
The same players are the one's saying, "these abilities are worthless" When the truth is they are just not creative enough to make use of them. i doubt the average PvPer rarely think to themselves, "Okay, that player SHOULD have whipped my #$%, cause they're just that good". I'm not going to say that the abilities are completely balanced, but it doesn't seem to matter at all to some players ~ because they're GOOD.
Adding AC's to the game, would create more 'perfect builds" for these players to "discover". There will always be some specs players elect not to use. But extra AC's with unique spec active abilities would still add variation to the game for both PvP & PvE.