The only talents that I am aware of thy don't stack are the ranged talents (neither actually affect ffb I believe anyway).
If you are putting together a ffb build for raiding it has already been covered in a thread that is linked in the greatest Mage post ever at the top of the forum. For ffb you want frost and fire talents. If you are going to be using fireball (fb) then fire + arcane (ttw) is the way to go - also discussed in tgmpe.
Oh and to answer your questions about the slow, it benefits from permafrost, can proc frostbite, and works with shatter. Come to think of it both threat reducing talents may not stack, I can't remember but it has also been talked about ad nauseum at elitistjerks.com
Edited, Dec 13th 2009 10:40pm by Anobix