Dark Mind is only good against magic damage, and not every tank buster is magic based so unfortunately it takes a bit of memorization to properly utilize when this skill is applicable or not.

In general, I would just use TBN on a buster and if you feel like you need more, TBN + Rampart stack really well for taking big hits. Shadowwall also works though I kinda treat this as a back-up TBN incase you need it and its on CD or your out of mana. Then once you've gotten a hang of what damage is what from a boss, you can start replacing Rampart with Dark Mind if its applicable.

In content before 70, Shadow Wall will be your go to for busters.
Repraisal is better used on teamwide attacks as it will mitigate damage for your entire team, and later on you'll get an ability called Dark Missonary(lv 76) which pairs really well with it.