It's not just the damage, though. Taint is generated too fast to be meaningful and the tanking ability of summoner needs looking at, too. There should be some downside to having good damage - And it'll be good even when nerfed. I don't think +2 con and +15% sip should be on one class, because it's too much of a tank buff and means with a highfavour an unartied summoner is rocking 500 health as intelligent, with notably stronger sips than others.
As for Bard, it does need nerfs. I'm not even going to talk about it in this thread though, heh.
This is exactly why the dirk was my first big artifact. People said they sucked, but the ability to push affliction rate well past what people could hope to cure was amazing. It still is. Some small efforts have been made to temper it - when illusions were still a thing and changed to allow two sets of illusions per dstab, they weren't tweaked to let fast statpack plus a level 3 dirk get in two illusions, so that slowed me down a tiny bit.
But as long as the dirk exists, the renegade and saboteur professions will be in an awkward situation where they're either balanced so the dirk isn't disgusting, and suck without it, or they're ok without it but the dirk renders them unstoppable.