I've hit 90 with my priest recently, and was thinking about the sad state of Mind Spike.
It is pretty much useless in it's current state (at least in PvE) outside of FDCL procs (If you picked that talent)
I understand Blizz doesn't want us to spam MS as part of our regular rotation, but i think it could use some other fix instead of giving it horrible damage.
What if MS had charges? 6-8 charges with a 5 second recharge rate, reduced by haste. It would still consume our DoT, but it could be used to rapidly burst an enemy down, and since it has charges, we wouldn't be able to spam it for long. It would give us about 10 seconds of burst when mobs are dying fast, or whenever we need it.
Or give it a high mana cost. So we can't spam it forever without going OOM.
Or a reverse Arcane Blast mechanic. Make it deal heavy damage at first, dealing reduced damage with each subsequent casts on the same mob.