As others mentioned before:

It is recommended, (if not mandatory) to get Cleric Stance, Protect & Swiftcast. These are not only QoL buffs, some can even change a fight (e.g. insta rezz).
Furthermore, if you got a grip on stance-dancing (knowing when you can dps in cleric and when you need to switch out of it), you can improve the dps of a group and let expert dungeons run smoother & faster.

Just a side note, if you are not sure about the mechanics of cleric stance: It swaps you INT & MND stats and furthermore increases damage from spells/abilities and decreases healing from spells/abilities, in other words you need to pay attention, because it will significantly decrease your healing output, while significantly increasing your damage output.