Warlock can soak with dark bargain, mage can soak with greater invisibility and hunter can soak with deterrence. Having a rotation of Hunter -> Warlock -> Hunter -> Mage -> Hunter -> Warlock -> etc.. should work out for you. Hunters can also soak 2 times in a row with readiness if it's needed.
Also, druids can soak single sparks with displacer beast, mages can aswell with blink and warlocks can with their demonic circle.
You have enough cooldows with 3 of you members
Hunter - talented deterrence
Mage - greater invis/cauterize and ice barrier/temporal blink
Warlock - dark bargain and unending resolve and portal
Disc priest can help with pain sup.
Remember there are 3 rages, 2 strengths and 1 courage per rotation and each rotation is 2.5 minutes apart.