No it's not a good thing, because you SHOULD be standing behind the boss most of the time, which makes it a waste of stats. Sometimes it cannot be avoided though (shado-pan trinket I'm looking at you).
The only boss you cannot get behind is Tortos and he doesn't parry.
Not a good thing, but not something you should dwell on. It's not completely useless to be over the cap. I think being over the hit cap is better than being over the expertise cap though.