There are some good tips that can be found in the tank role and healer role forum groups. I can say for certain that for paladin you'll want to level up marauder until you unlock mercy stroke. If you pursue conjurer to lvl 32ish you can unlock stoneskin which can help yourself in solo content. If you want to pursue conjurer all the way through white mage you'll want to work on thaumartage to unlock swiftcast. Hope this helps some and definitely go through the role forum groups, the conversations have a lot of good tips in them.