I've built a few healers over the years, always as NPC healers for the party, but always too with an eye to making them fun to play.
I think healers are even more viable in RMU, for the most part. The main improvements that RMU offers (over RM2) are:
--Spells: Healers have many more powerpoints available for spells and can cast spells of their own level or below without preparation, which makes a healer much more fun to play: there are far fewer rounds spent doing nothing but spell preparation, and many more rounds in which you can cast spells.
--Weapon Costs: In RMU, both Healers and Lay Healers can now actually afford to buy two ranks per level in a weapon. The weapon skill costs have been reduced from 9/20 or 8/20 to 5/7 and 6/8, which makes a Healer/Lay Healer a much more viable combatant. Really, you could take two ranks/level in a melee weapon, use spells for your ranged combat, and be a very capable combatant altogether.
The only downer for healers in RMU is the Footwork skill, which costs so much for healers (9/12 originally, though I think down to 7/10 now) that it means you really can't move at all in combat without taking significant penalties, and thus really cripples any attempts to make a healer a viable melee combatant in RMU. This is the main reason we have just removed the Footwork skill altogether from our RMU games.