Upgrade that gear. That will help.

Aurum Vale is a big heal check. It rolls out damage hard, and the other players have to watch the different poison stacks themselves and eat fruit accordingly, are they start melting. If they wait too long, there isn't much you can do.

AST at that level is very underwhelming DPS wise. Card use should make up the difference with the party.

You get two very useful AoE skills later, Gravity (which is similar to Holy) and a unique spell called Earthly Star (you drop it like a zone on the ground, but as the clock ticks it gains power. When you set it off or let the timer finish, it has a huge burst of enemy damage and party healing on anything thing in the zone.) At level 70, AST does perfectly fine with doing damage amoung the three healers.

Honestly, other than your gear needing an upgrade, I can't see anything wrong other than AST is meh at that level and Aurum Vale can be painful.