It's kind of hard to give advice without knowing what difficulty you are playing, and who is in your party.
Is your team max level?
Did you make sure to rest at one of the better inns for solid bonuses? (Celestial Sapling in Hearthsong or Dracogen inn in Dyrford Village)
Did you much a bunch of food before hand? (also potions are instant use in fights, highly recommend having some key potions on characters to kick off fights - like potions of power, potions of deleterious alacrity, Llengrath's displaced image).
Pretty sure the constructs are also vulnerable to weapons like St. Ydwen's redeemer, it doesn't even need to be leveled for the change to destroy vessels proc.
While all 3 targets are very resistant to quite a lot, they aren't necessarily immune to key control effects. I had two characters pumping put as many AoE paralyzes as they could to try and keep things under controlled. Cipher's Mental Binding (L2 power) is one of my favorite abilities. Try tossing out some debuffs like Priest's Shining beacon & Divine mark.