I feel your pain took me 5 failed attempts to stop and think of a decent stat, i suggest leveling to 50 as you get a crit chance dps cd which is nice if ur shield spec. (stockstrike ftw)
I found strat wise it was best to agro a single guard first and drag him around the pillar losing the two targets and making dorne take agro from the other. Then when dorne was at say 40% id taunt. Id constantly kitie around the pillar preventing them from healing each other often letting dorne take agro of the guard i wasnt focusing.
use your small cd interrupt to prevent the focused target from healing whilst using cryo harpoon combo (Harpoon to interrupt the first heal then cryo the next at which point u kite your focused) to shut down the other. Dorne also helps with the interrupts. When the main target gets to say 30% pop dps cds cryo the other then if your shield spec storm to it after the cyro is down to interupt the heal, then harpoon the other to you use your 20min cd heal to refresh cryo, cyro non focus and after that they main should be dead or close too. Once thats done you,ve won.
The other guard goes down easily without his mate and rak himself is a joke
With non shield specs it tweak the strat to be less about controlling the other guard as you would have more dps.
Sounds like a nightmare but it really just involves cycling your interrupts carefuly.
ONLY use your interrupts for the heal you wont be able to interrupt them all but you will able to interrupt enough to stop them out healing your dps.