Do you scan enemies for weak points? Just abuse their elemental weaknesses and if they have heavy weapons attached like the disk launchers on the Thunderjaws then take those out first, many times which can be picked up and used against them. That and abuse your rope and trip casters.
Yeah, I'm hitting the corruptors with fire arrows because their weakness is fire then hitting their weak spots with normal arrows. Takes forever, there's two of them and I haven't even taken one down after more than thirty attempts. It's the scene with Olin and all the snipers.