Actually, all the sets except Torag have some use.
Ahrim - best magic attack before Ancestral;
Dharok for "dharoking" (hits insane damage if you are at 1 hp, which you can artificially keep).
Guthan - to keep you at a slayer task without food, also for getting Fire cape (you won't need any food or sara's at all before Jad)
Verac: in full set you hit through prayers or defence. This way I've managed to kill KQ and Chaos elemental for diary, way before I could do it normally. Also the skirt and helm are good melee/ranged protection, people sometimes use one of these in some combo armour when you need everything at once.
Torag... sell :)