The key issue I see with most of the AST's abilities is that they're too situational, and that includes many of the healing options and nearly all of the card buffs.
I'd suggest making the following changes:
Bole: Make the buff last 1 minute and have X charges, where the target takes 10% damage less from the next X hits until the buff expires or runs out of charges.
Spear: Make it reduce cooldowns that are already ticking instead of just ones activated while under the effect of Spear. I pretty much always RR this card because of how massively situational it is. Even if I DO have voice chat, interrupting the party to ask, "Hey, does anyone have a cooldown they're about to use?" is crazy, especially since DPS don't usually hold onto cooldowns and even when they do, you have no idea when you're going to draw the Spear.
Balance: 10% more damage AND healing would be nice, here.
Arrow: Fine as is.
Ewer/Spire: Instead of reducing the T/MP spent for 20 seconds, just have the card restore X% of T/MP over 20 seconds instead. There are just so many times when a player either:
A) Won't notice the Ewer/Spire is on them.
B) Won't be in a position to actually use their abilities due to raid mechanics singling them out.
C) Won't be in any danger of running out of T/MP (and we cannot even see TP bars).
If these cards restored X% over 20 seconds, then A and B will no longer matter, if they're near full and spending T/MP, it'll get restored as they spend it. If they're NOT spending it, it'll be restored if they have it missing, and while they may not notice that the buff is on them, they'll DEFINITELY notice that they have more T/MP when they glance down at their bars.
Collective Unconscious: It seems odd that a healer with a lot of mobility has a channeled ability like this. Instead of making it placeable like other healer bubbles, let us run around while channeling it. That would actually make the AST unique in their ability to reposition a healer bubble while casting it and make it less situational as you don't have to worry about having to run out of AoE a moment after you use it.
Disable: Make it not proc on auto attacks, only actual abilities. Bosses apparently auto attack while casting things, meaning that your attempt to weaken their next attack will likely fail.
Luminiferous Aether: I'd reduce the cooldown to 90 seconds instead of 120. AST already suffer hugely with mana management, especially if the DPS take avoidable damage.
Synastry: Possibly the most situational ability in the AST's toolkit. Only really useful if you intend to throw it on a tank and then single target heal other party members. What if, instead of doing this, it either smart healed the nearest injured party member for 50% of the healing you do on the target, or did some kind of AoE heal for X% the healing you do around the target? AST suffers from a lack of emergency options as it is, and this would give them some way to heal the rest of the group while focus healing a tank.
Lightspeed: For a 150 second cooldown, does it really need the 25% reduced potency?
I think the AST suffers mostly from a lack of emergency options, and if they're going to be queuing as healers via the DF, they're going to need to do a bit better in handling parties where players get hit a lot.