Important stats by Roles

A little help to what stats you want to aim for depending on your game role.

Stats for Tanks

Tanks should try to have all of their defensive ratings, and possibly Power, Combat Advantage, Forte and Incoming Healing match their TIL. Having some Accuracy would also help building aggro a bit more reliably, but it's less important than the other stats mentioned earlier.

The top priority stats to focus on to 90% are Awareness (first and foremost), then Defense (after Awareness but before every other stat), then Critical Avoidance, and Deflect Stats (starting with Deflect, then Deflect Severity, as you obtain the best returns when you cap Deflect at 90% when your Deflect Severity being 55%). Improving Power and Combat Advantage together would also help with building aggro. And improving Incoming Healing would help your healer.

Stats for Healers

Healers should have Power, Outgoing Healing, Critical Stats, Forte, Defense, and Awareness match their TIL. Critical Avoidance and Incoming Healing would also help. All of the other stats are meaningless.

The top priority stats to focus on to 90% are Power and Outgoing Healing (together for best returns), then Critical Stats (together), and Forte, followed by Awareness and Defense.

Stats for DPS

Out of the 15 stats, Damage Dealers should try to have all of their offensive ratings, plus Defense, Awareness, and Forte, match their TIL. Incoming Healing and Critical Avoidance shouldn't be neglected either. But all of the other stats do not matter.

The top priority stats to focus on to 90% are Power and Combat Advantage. Once these are capped, Critical Stats (with Critical Strike = Critical Severity for the best returns) and Accuracy are the next goal. If you can still increase your percentages after capping your offensive stats, then Awareness would be the one, followed by Defense.