Also, I've noticed that the lilly system work super well in those kind of instances were trash mob hit like trucks and every one is undergeared as you will certainly use single target healing spells a lot. Minding your OGCD usage to have them come back sooner can be a life saver.
The idea is to use the longer cooldown first so you can use them multiple time during the same pull and keep divine benison when you only have 1 lilly. Also, pay attention the what kinf of CD the tank is using. For exemple using holy to mitigate the damage is good, but using it when sentinel will lessen the effect.

WHM clearly is the best dungeon healer, and maybe one of the best dungeon class period.