I don't have that GX thing on Athena so dunno. As far as GS sets go I already have my end game set all sketched outNot necessarily, it's not difficult if you use Athena's ASS and know what you are looking for on some level. My general use mixed GS set has
Challenger +2
Critical Draw
Rock Steady
Razor Sharp
Focus
and 4 slots (one with torso up) so that I can get any 5-slot skill such as Tremor Res, Bio researcher, Mushromancer or similar.
Granted, this set uses two GX Hunter pieces, so it will not be possible for most people until another month or two. It's still far beyond what you could fit into a SK set, and it's essentially SK without Rodeo God and Mind's Eye, and Mind's Eye is useless against most monsters in endgame.
In most cases the sets won't be that versatile, which is a strength for the SK set. When you have found your end game weapons though I think it is more useful to build custom sets for these weapons specifically.
Sheath Control
Sharpness +1
Focus
Critical Draw
Challenger +1/+2 (1/3 weapon slots)
But I'm having a lot of trouble getting a lance set with Athena.