Well I only went and did it! Ornstein and Smough are history!
Things just werent working, so I swapped my armour and weapon choice, did a little level grinding, summoned a little help and switched up my tactics. My summoned helper (who I shall name Keith) kept Smough busy whilst I took down Ornstein. Keith died in the process but it was just enough to get me through to phase 2 of the battle.
The empowered Smough still wasnt no cake walk, but I took it slow, picked my moments to strike and took full advantage of the cover provided by the pillar bases. I took a few hits and depleted my estus flask, but after a long 10 minutes (it felt longer) it was all over.
Raising my level and sinking a few points in to endurance certainly helped - my character build could finally wear a decent set of heavy armour without feeling like he was wading through quicksand. I was starting to get concerned that my lack of ranged attacks was going to prevent me beating this boss battle but in the end I didnt even need it.
So, Im back in love with Dark Souls again! It feels good.