I suggest that there be a combination of the buffer and the healer (or a separate npc). why? I personally think that it causes a downtime to moving around. A separate NPC would be nice. It would automatically deduct zenny from you while providing buff and heal, probably a premium npc that you have to one time buy with cash points to access?
An instance warper < just warps you to certain coordinates near the NPC but not give the access to the instance if you don't have the prerequisites