What makes mystic underused is the fact that they're almost useless in PvE.
Their skill cooldown are too long and in the meantime they inflict almost no damage compared to other units usable in PvE.
Some guardians have party shield and taunt/misdirect which makes them usable, but mystics don't. What's funnier is that most of their skill effects are RESISTABLE by bosses which only make them totally useless in high-end PvE.
To make them good, they should be buffed in PvE; because some mystics are already good in PvP.
Some of my suggestions would be :
- Convert some mag stat into atk, so mystics can deal decent damage while waiting for their skill cooldown, if this mechanic breaks the balance for PvP, give another mechanic to cope with mystic's weakness in PvE, like -2 skill cool down per turn in PvE, or give another effect of mag stat (like extra magical damage or % skill effect increase).
- REMOVE RESISTANCE FROM BOSSES, FOR GOD'S SAKE. WHAT'S THE POINT OF HAVING DEBUFFS IF HIGH END BOSSES SIMPLY RESIST ALL DEBUFFS ?
ahem. Resisting stun, sleep and charm is common, but resisting poison, atk/def debuff, and also hex is simply ridiculous.
- Doubles the healing effect in PvE, but lowers the healing to 25% in PvP, so that the current healing effect stays the same in PvP. Also, lower some skill cooldown. 6-7 turn skill cool down is too long, in 7 turn, it's either all allies or all enemies are dead (what's the point of having a healer then? A healer who can't heal is like a dysfunctional society member).