Really the only KB I think that shouldn't work on Guardians is the ranger KB trap. Everything else is fine. And it'd be nice if Shield Bash could be feated to KB full plate.
Shield bash was really nice back before DT and Conq could wear fullplate. It pretty much was a guaranteed KB against anyone aside from rogues that were good enough to pop excellent balance and other guards. It's not quite as effective as it used to be these days, but it's still a solid KB.
just wondering if lower ranks of stagger and SB are as effective as the higher ranks, specifically could I use rank 2 stagger and SB at 80 since they seem to have the quickest animation.