just spitballling.... but if you are at 300 skill, that is like a 19 level jump to a level 100 mob for an A+/- ranked weapon. Might be a bit too big of a gap for a consistent high skillup rate. 80-ish skill should move along fine in abyssea, maybe scars areas? That's pretty much where I've done my skillups once I hit 290/300 levels--in Abyssea zones.