Interrupts are one of my favorite topics of late, actually they were before they were buffed. I also play a build using Chaotic Interruption as one of the centerpieces. I believe interrupts are absolutely viable, but you have to keep in mind what game mode we’re talking about – PvE/PvP/WvW. The sentiment can be quite different in each. On the other hand, I completely understand the desire of those who want to have more control over interrupts with instant cast and easier to read skill animations. I played mesmer in GW1 and loved that playstyle. GW2 is just so different though. Anet obviously has other things in mind with interrupts and they definitely have their place. For instant cast, you can’t forget the daze mantra; traited, that’s three on cast interrupts at your fingertips with 5 sec CD in between. Hard to beat if you’re after a pure interrupt build. There’s also Magic Bullet, which I would consider a valid on cast interrupt for the medium to slower skills. Of course Into the Void can absolutely be used as a timed interrupt, but most good players know to dodge or avoid it. So it’s not like there aren’t instant cast type options, but I agree they could be improved, for example, signet of domination.
For group combat, honestly who is going to really be focused on interrupting on a single target? More thought will spent on tactically gaining advantages with the group in mind. While timing an interrupt can indeed help, you’ll get much more mileage out of taking Imbued Diversion and shattering a single clone bomb on a group to possibly proc multiple interrupts. I know it’s the “possibly” that irks many, but RnG has it’s place for sure and that I believe is intended.
So, yes I think there is a balance to strike here somewhere which hasn’t fully come to fruition, but if you slow the game down too much, it’s not as much GW2 anymore.