i've only just started playing last week or so, i'm at like, GS 465 or something, but there seems to be a little bit of a weird range where like, 15 GS can make a huge difference. like when you just start a new world tier, everything has a nice challenge to it, but then after you get a couple of new pieces it goes back to being "normal" difficulty pretty quick, it seems. i mean, honestly the only time i found the game actually interestingly difficult, is when the black tusk show up, because the world is a higher GS now and it's a completely new couple of enemies types. but again, once i got some new gear pieces, they really aren't any more difficult than anyone else.
i'm wondering if the reason why they aren't adding a higher GS level is because then people can't "outlevel" the raid. no matter what perfect gear combination you get, they'll still be higher level than you.