Someone has apparently worked out the rotation of drakes on the halfus encounter, which means that this week will be:

Nether Scion, Slate Dragon and Time Warden.

This means the boss will have:

Frenzy
Mortal Strikes

and the Proto-Behemoth will have:

Fireball barrage (Small AoE, deals ~40k damage to anyone within 4 yards)

So the strategy for this week will likely be:

Release + burn down Nether Scion (Remove frenzy and reduce damage done by boss by 25%, as well as reducing chance to hit)
Release + burn down Slate dragon (Stuns halfus for about 25% of the time)
Release + burn down Time Warden (Makes fireball barrage avoidable)

The Slate dragon being present will necessitate tank swapping (BoP would be useful here again), and the Time Warden will mean the DPS cannot stack on the healer - if people spread out this will result in less raid damage than the fire breath enabled by the whelps, albeit concentrated on one person.

The rotation theory/orginal post is here:

http://www.mmo-champion.com/threads/841742-Theory-Halfus-is-not-Random

If you're interested in the combinations.