I would have thought lighter strings would make it worse. I would try raising the action at the bass end slightly.
Quote by littlemurph7976
Maybe try using .12s?

That would worsen the problem; 13's are tighter under low tunings.

You'd probably have to do some work on the truss rod, the action, the intonation.... do you plan on keeping it a Drop C guitar?
Yeah, the pro was right - ridiculously low action with thick gauge strings isn't possible without some fret buzzing. You can raise it a tiny bit and eliminate fret buzz, and not really notice a major effect on playability.
Ibanez RGA121 | ESP LTD H-1000
Axe-FX Standard
Quote by ASClark
yes, it will be in drop c or d standard almost 100% of the time. i had the intonation and action set up by a professional yesterday, but he said the buzzing would be a problem if i wanted to keep the action low

Right. Then, as the guy above me said, raise the action slightly through trial and error. Just a little bit at a time, until you're happy with the amount of fret-buzz AND action. You can't have the one without the other...