High tier delves are hard. But I’ve discovered a few things that make them a lot easier.
First, set Brann as dps and rely on your own heals or survivability. Brann is a terrible dps. He’s gonna ruin los pulls, and sometimes make life harder. But he does interrupt casts, and his damage helps. Also, knowing that you can’t rely on his heals, which are unreliable from the beginning, changes your mindset.
Second, mobs aren’t linked. Even packs, or mobs that are standing practically on top of each other. You can aggro one without aggroing them all. Take your time, do pulls you know you can handle, and it becomes much more managable.
Third, learn which casts are worth kicking, and which abilities you need to dodge. A general rule for all content it that if the move is telegraphed, its gonna hurt to get hit by it. So pay attention.
Hope this helps. Enjoy.