Umm..Thunder?

[Vortok]

Run dungeons, the exp for them just got boosted (to probably be better than FATEs). You picked WHM so that you could primarily heal, right? There's a new one every 3 levels starting from Braylox (4 level gap for the two previous to it) all the way to 50.

And unlike FATEs, dungeons will actually give you gear. If it's your first class, there's plenty of side quests/story quests to help you level as well. Most that involve killing stuff are only a couple enemies so killing them without Thunder shouldn't be too hard. Not really any 'kill 10/15 of X' that's so common in MMOs (unless it's the Archer starting quests, lol).

Remember to use Cleric Stance when you're killing stuff. By now your Mind should vastly outpace your Intelligence, so it actually makes a difference now whereas when you first got the ability it probably didn't impact your damage at all. If you get bored in dungeons, you could throw it on and cast a few damage spells before turning it off and topping people off again.