A suggestion to reduce stress on healers:
Make all healer attacks dependent on MND, not INT stat, removing the need to dance in and out of cleric.
That way there will be less downtime, and it would be faster to react to incoming damage to the tank. Those that do not want to dps can still just heal, while those that do want to dps and heal can do so.
Edit after the discussion:
Counterarguments:
Point 1: Cleric gives a 10% damage buff, 20% healing reduction (on top of attribute switch, disabling healing for all intensive purposes). To keep the balance with other jobs losing that 10% might not be too bad.
Point 2: Cleric adds a level of complexity to being a healer, a sense of danger...its been around for a long time, so people are used to it now.
Point 3: Cleric is what makes healers good...even if thats only one piece of a puzzle, other than knowing the encounter well, being able to handle large pulls, undergeared tanks, multiple dps eating the dirt, stray mobs attacking you, all while dodging aoes, controlling your fairy, shields, card buffs, etc.
Point 4: You are asking for nerfs. Not really. Its a shift in what attribute is used, attacks still have a cast time and cost mana, healing is still the main task.
Arguments:
Point 1: Cleric does suffer from lag, meaning sometimes it doesn't come off fast enough.
Point 2: Accuracy penalty is still there. It doesn't feel particularly good to switch to cleric and toss in a mana-costing skill that just misses, even if that only happens on occasion.
Point 3: Cleric became a metric for judging healers, and that's not a good thing. MND base would make it less visible if healer tried to weave in dps or not.
Point 4: Removing cleric would give WHMs space for another skill.
An Alternative Idea:
Remove MND/INT swap that cleric does (with MND being the new stat), while keeping its 10% damage up and possibly increasing the healing penalty from 20% to 50%. That way there would still be a need and a risk to dancing in and out of cleric, but out of cleric healer dps will be more potent than it is now.