The Icedome is a difficult area with many clumped and packed groups of hex dealers and other Summit foes, and you might be attacked as soon as you enter the area. Careful pulling, however, should make short work of the mobs as Dolyak Masters are rare. Keep alert and this area should present no real challenge.
Beware of the tightly grouped Stone Summit groups at the center of the map (blue circle on the map) as you can easily overaggro here. Take out one group at a time to prevent a party wipe.
There is a small group located very close to the portal to Frozen Forest (green dot on map). It is advised to pull them with a longbow from the portal, because AoE spells can cause them to flee in the portal and vanish, thus preventing the area to be vanquished.
There are only four Dolyak Masters and you will never encounter two in a single group, so consider to take them out first.