I agree that quicksand is a bitch kitty. I also see what you're saying about the logs, because I read them too. I think that the impression is skewed a little because of the people that are currently active in Fort. They have two level 51 invokers. That's what they're gonna do. Unless they are inside where you get double nova. The same holds true with the Spire right now when both their necros are on. It hits less often but they are gonna come with PWK when defending. That's what they do. Still, that's what they have active quite a bit is those 2 necros, the dwarf shaman, and the shapeshifter. I think you just gotta understand going in that's what will happen.
I personally don't know a way around it. I don't know how to beat it. But without it are invokers viable for stuff? I don't play vokers so I don't know. We see the damage output but without quicksand are they still something people would want to play? I think that is what you have to consider when you talk about taking a power away.