Have you tried ad marks and hybrid quints? Also i wonder if you've tried the Lizard Elder build. Though this is meant for jungle, it gives great ad damage plus mana reg but more than anything else the unique passive synchs with your q and makes your damage levels go up incredibly--it also synchs with the above marks and quints, as well as rylais and morellomoricon sp), and zeke's herald as well. I've been experimenting with Soraka w/out gold quints and as a support...put up a quick guide and it got blown out of the water (Hybrid Soraka SOP)