I'm having trouble finding any reason to spec just far enough to get the Felguard, then use the Imp. Basically this is a case of you failing to exercise either common sense or the Search function.
Maybe I missed it somewhere, but I haven't seen anything on Felguard vs Imp with the 0/41/30 3.1.1 builds going around. I would assume felguard would be the way to go, but I just want to make sure. I currently run rDPS meta since we don't have a (reliable) ele shaman. But I've been toying with making my second spec 0/41/30 in case he actually does show up for a raid.