If you prefer AST:
- Synastry is a nice +healing boost.
- Try not to overlap cooldowns if possible.
- Regen stance helps versus SMN teams, otherwise I prefer shield stance.
- Assist enemy dps as often as you can to watch for dps swaps.
- Keep your mana regen abilities on cooldown so you reduce the odds you'll be out of mana.
- Stella is very nice.

IMO, learn WHM. Sleep is too good in the current meta. Aether tanks and dps usually do not Purify you when you're slept/stunned (<3 the bards who Paeon). Countering their Sleep will help break up the pressure.

Our aoe stun can hurt tanks/dps when they are waiting to time a stun.