One other piece of advice to help the healer pull less hate: Make good use of crowd control! An enemy that isn't hitting the tank is an enemy that isn't making the healer grab more enmity. Sleep is the most effective tool, completely halting a foe, but a good number of enemy types are downright immune to it. Conjurer get Repose, a single target sleep, at level 26, while Thaumaturge gets Sleep at level 10, and upgrades it to an area version at level 36.

When facing enemies that cannot be slept, bind works on just about anything short of a boss. However, this only stops a monster from moving, and as such is ineffective against enemies with ranged attacks, or if they are bound next to the tank. Fluid Aura works as a short-lived solution, both knocking the foe back and binding it, albeit for a mere 6 seconds. Summoner gets a 20 second area bind, while archer gets a 10 second single target bind.

Note that in all cases of crowd control, the effect is removed if the monster takes any direct damage. However, this does not include damage over time. Not only does this mean that DoT effects already on a monster do not stop it from being slept/bound, but you can also use any skills that inflict a DoT without actually doing damage from the skill itself. Namely Bio, Bio II, Flaming Arrow, Shadow Flare, and Bane.

Finally, if using crowd control, communicate with your party members. Players should avoid using area attacks, and summoners should use "order" to stop their pets from using area attacks as well. For those concerned over the less damage this way, it's useful to note that a skilled healer will use the time and MP saved by not having to cure as much to deal damage instead.