To add on: Belle Snow is considered great for World Bosses because of her attack and defensive buffs, same reason Ravengale is.
I'm going to disagree with Limit and say to make Turq into Draco Brightspark first. Blackaria's awesome and you definitely want to get her eventually, but it sounds like it might be a while before you're leveled enough for GB. You're good on healing right now, and light on AOE damage and crowd control. DBS is a damage + crowd control house, and you won't miss Turq's sheep. And if you want to go ultimate for GB, she's good for that too.
After that, I'd go for Kymael (using Ari). Her resurrect on death works very well with Shabelle's resurrect, and she brings more crowd control and protection.
Keep in mind that some special deities need a special class of character to ascend from. Keep your Paladins and Incanters around if you can.