The vast majority of players want you to keep the bubble stun, but:
A) Can't click the buff icon to pop the bubble. A spammable AoE stun that barely affects resolve is total BS.
B) Can only be applied to self, or:
C) Give it a much longer CD.
Chain bubble stunning should NOT be a viable tactic in PvP.
Chain bubbling stunning shouldn't and isn't happening. I mean, unless you are going to tell me the bubble stun doesn't fill resolve. Honestly? I've never noticed. I just assume. The deioniziation (CD) on bubble is 17 seconds at best, which means if you are spending 3 seconds of it stunned, you're still up for 14 seconds of it.
I do COMPLETELY agree with your first point though. This cancelling it for stun on demand - no, that specifically should be patched ASAP.
If it only applied to the caster, again it'd really negate the value of the adv class. For DPS spec sorcerers, it does function like this.
it's really more about the healing sorcs. 31 point healers are still of low value in rateds as I currently understand it. The whole point behind having healing hybrids is because the main spec is meh. No CC, just a turret healer with modest escapability. That big AOE isn't saving anyone's life under pressure, it would need a 50% healing buff to be of any major value - and all of their/our relevant heals are channeled, a stationary target for stun/ lolsmash.
I'm not quite sure what the proper solution is. The quick and dirty would be to drop the stun time from 3 seconds to 2 seconds.