Well, I'm a main AST now and I had pretty much the same issues while leveling my WAR.

One thing to notice: If you didn't level your WHM, it's extremely recommended that you get at least to Lv34 for Stoneskin. It will be a great help.
I'd also recommend Cleric Stance, Protect, Swiftcast and Aero.

As for the feeling you're not up to the task, maybe it's because of gear. After leveling my 3 healers I didn't have lots of tank gear, so I had to go through dungeons undergeared. Because of it, I pulled less enemies and the dungeons took longer, but safe. But in your case, the tank may or may not feel comfortable while leveling and do large pulls and you have to deal with it.

Don't be afraid to use Synastry, ED and Asp Bene. Save your Boles to the beginning of the pulls. And if you feel like your tank is pulling too much, let him die and he will realize it heheheheh