For the record, on my DRK alt I never have trouble against Hally's critical hits.

1) Awareness 15 seconds before pulling
2) Shadow Wall
3) Awareness as Hally starts channelling the 2nd Queenly Waltz
4) Shadow Wall
5) Awareness as Hally starts channelling the 1st Holy Spellblade of final phase
6) Awareness on Critical Hit (no point in timing this one)
7) Shadow Wall

If I'm nervous, I can use Rampart to cover certain high damage phases (Like Holy Spellblade on me, or specific critical hits). TBN is preferred for Critical Hit, but not always needed, depending on how good the healers/offtank/melees.