WOW PowerLeveling: I started going on Elder Mammoths before level 90
Where to level? Now that's a easy one - you level where your party wants WOW PowerLeveling to Good thing about Cleric is that you can be lowest level in party and still contribute the most (just make sure exp division is equal if partying with *much* higher level people, or risk doesn't compare with rewards).
Example, I went to GoS below level 60 and did pretty well there - it all depends on party members. I started going on Elder Mammoths before level 90. Astarots - below 100, your level is not important, your party members are, and your buffs, obviously.
Purify - it might seem a waste at first, since there aren't many debuffs worth dispelling, but you will appreciate it when your main tanker gets surrounded by enemies he could easily tank normally, and then gets - DEF and – AVO (tested *many* times against Goblin Guardian as well as Astarots.
Helps against Tirwins/Elect Ghost as well, even - DEF from BK. 1 level won't hurt (much). Also, certain monsters on Eldeon use Silence - so if your main fighter gets silenced, you know what to do.
In temple, your summons can deal significant damage and actually let you get kills (especially if you have Summon Mastery level 2 allowing you to summon 2 of them).