I prefer the healing aura idea. heals x hp based on skill level and effects all friendlies within x feet where x is also based on skill level. min requirement could be like 750 d healing. for every 100 in the skill it heals an extra 0.5 in 4 seconds and extends its reach 0.2 meters. maximum could be like 1000 hp in 4 seconds reaching 20 meters. uses x mana every 4 seconds as part of the healing process.
you could also add in a new sort of mana drain, un-regeneratable mana. every mana used by an aura could only be replenished by vials. sleeping and meditating wouldn't raise it. this would be in effect to stop the aura from lasting forever due to mana regen or meditating while using it, players would have to purchase vials to keep their energy up.