Kinda off topic, but the question was answered effectivley. The simple answer is Shield Block. Keep it up more.
I'm sure it's been posted or mentioned in the past or a different thread, but it's worth noting.
Consistently, we use a Shadow priest with some AResist ( Trink and pants ) for the Bolt tank. This reason is multi faceted.
First, the SPriest can keep a more consistent spell rotation up on curator, as opposed to the flares who should be dead withint 7-9 secs, or less. 7-9 secs is hardly enough time for a SPriest to get a good spell rotation in.
Second, with the priest focusing on Curator, he/she is able to keep VT and VE up and use it's effects more consistently and more mana efficiently. When/if the Spriest catches up to the tank on threat, ( Should stay well below the tank but above all others (healers) allowing for Heavy Evocate damage) He/She can switch to MB or MF the flares to help get them down faster as well, thus allowing more DPS to hop back onto curator between flares.
This strat allows for this fight to be done with one healer ( pref. druid for mechanics of the rest of the instance, poisons and instant HoTs on Aran ), and he rarely hits his 2nd Evocate anymore. If he does, he's guaranteed toast.
If there is one thing I have learned from the WoW forums, it's that you can't keep someone with no shame down.