I think its needed honestly. I haven't reached endgame yet, but I know I'd be aggravated if I waited to get into HM Titan only to get a tank who was wearing a bunch of level 30 gear. I also like to be prepared for that kind of thing, knowing what ilvl is needed helps me figure out if I can pull my weight in a fight or if I'm simply not ready. I might be wrong, but I imagine this will be restricted to DF so you might be able to form your own group with that tank in level 30 gear.
My problem with gearscore is that you get people trying to put groups together that will refuse to take you unless you significantly outgear whatever it is you're trying to do. Of course people will always do this, I've already seen those type of shouts.