I would actually prefer the cooldown, but a shorter one, for both enabling and disabling it.
Often times I'm mashing it to turn it off and end up turning it back on. Oops!
But in regards to the topic, I would like to see healers encouraged to dps more often, rather than stand around waiting for a time to heal. It really keeps the flow going and, in my experiences as a healer, adds more fun and excitement than it is to stand and do nothing. In the end, it's optional, so both playstyles can work fine.
