I agree with Phish. To me it would be an all or nothing thing with buffs. Either clerics or classes have them or they don't to see any effect. Even if they are reduced people will still have buffs vs those without buffs. And the clerics that go all charm into CD die fast typically, those that have figured out a good def or hp build have a lot lower buffs but are able to still stay in and heal and support their team. The trade off is that the team has lower stats than those buffed with a full charm cleric, but they still have buffs and get the benefit of being healed and puried during combat. Plus a lot of the full charm clerics play the healing crystal game and don't really support the team anyway.
Maybe put the combination buff pots in the Honor shop so people can get the benefits of buffs without taking up their whole inventory and more will use them if they end up on a team with no cleric.
The healing idea is not bad. I play cleric to help support the team, so I obviously don't want my heals taken away, and at times I don't feel I have enough heals (even though we do have a lot of them), but I understand how heals can make or break a CD.