I feel like this encounter is designed to teach people about high ground advantage but I also feel like it assumes that you recruit Shadowheart first.
You are expected to click on the tutorial text and then it shows you where you should stand. If you stand where shown, the encounter isn't that difficult as it takes the IDs 2 turns to reach you and you are expected to use Shadowheart's guiding bolt to kill them before they reach you.
Warlock should also be using hex for extra 1d6 damage but no where is that mentioned and hex isn't one of the default spells either which is a separate issue.
Might be an L2P on my part with this one with the UI, but on point and agree.
EDIT: re-did the encounter, since I completely missed the tutorial first time around. Game changer, currently playing on a 43 inch monitor, and never even saw them until I read this post. Thanks!