To be completely frank, the tentacles do look like a fungia, they are flatter on the end than a duncan which has tentacles that come to a much sharper point. On the other hand, I've never heard of a branching fungia; Ive heard of fungia babies on skeletons, I've heard of tongue fungias, and weirdly shaped fungia, none of which were mutli headed single colony.
That being said, if I had to take a guess, that looks like a branching torch coral. Torch coral heads that are still young look exactly like a fungia - with their stubbier and rounder tentacles. Branching torches are pretty cool in themselves, but be warned that those tentacles will get long, and its nowhere near as rare as a "branching fungia" would be.
Hope this helps.