That's the problem, I'm playing pure INT. My only melee weapon is the starting dagger for ripostes & backstabs. That gives me no choice but to supplement my casting needs with pyromancy. I've gotten all 4 great souls but I'm still relying on the same spells and equipment I had over 100 levels ago.
Pure INT works perfectly fine with the Moonlight Greatsword as an offhand and that shield that has a C scaling with INT. Just need a few pts in DEX and STR, the latter of which you should have anyway to use a shield. Four Soul Vortexes and I can kill the Ancient Dragon, in group, on NG+. And I one shot nearly any idiot that tries to PVP me too, with a single Crystal Soulspear.
I'll probably dabble in Hexxes next, enough to be able to silence and make myself officially unkillable

Pro tip: Soul Greatsword can gank people hiding behind pillars or using stairs or doors to block LoS. Always keep one of those on hand. Oh, and I agree with others that Soul Vortex is trash.
Pro tip #2: You can stop your casting animation just before it starts with a roll, then cast again immediately to catch those pesky roll-twinks in PVP with a quick enough spell (Soulspear, usually). "Clipping" basically, ala DCUO.