endure is being casted immediately after releasing pokemon, the chance that cooldown will charge short time before pokemon dies is much higher than chance that any other pokemon will use its heal twice. Nobody casts aqua ring, healera or recovery wish/ingrain immediately after releasing, so probability that cooldown of these will charge before poke dies is very low. That's fair.
Just before you will sugges to increase cooldown - that won't happen, because it will be worse for people who are exping.