Rotface is more of a technical encounter than Festergut, it requires more proper execution rather than gear checking. On the same note though, Festergut is significantly easier encounter as far as mechanics are concerned.
As for two healer or three healer, if your group is geared like you say it is, it probably isn't likely that you will be able to two heal the encounters just yet. If you were a group doing ToGC Tribute to Insanity runs your healers may be more prepared and could potentially two heal the encounters. However if they are on the lower end of the gear scale, ToC instead of ToGC gear, then I would error on the side of using three healers.
Raids having trouble with Festergut's berserk timer should however focus on Rotface or Blood Prince Council as both are more execution based encounters rather than a DPS check.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.