Every healing class has an alternative heal if their main heal gets interrupted. Both sorcs and merc healers also get interrupt immunity cooldowns. Over half the HPS from an operative is coming from non-interruptable instants. The only way to handle it is to chain stun and burst, which is entirely based on which classes you have available to you in the fight on the DPS side as some classes cannot chain stun or burst easily.
What'd be interesting (but they won't do) would be if they gave PTs/VGs a 10 second no-regen debuff they could put on people to help break stalemates. For 10 seconds, you don't regen any energy and your existing energy pool is cut in half. Give a 90 second cooldown and make tanks immune to it. You'd fix the current PVP situation and VGs/PTs at the same time.
For sorcs/sages if you don't need to interrupt everything. If you interrupt innervate/healing trance, you'll cut out a large portion of thier healing and core mechanic. You have a point with the operative, many of thier abilities are instant. Emergency medpack is pretty insane for an essentiallly spammable ability but you just have to time your stun for when they are low.