Stensig wrote...
I am literally out of ideas of how to beat this guy. I mean one rogue is annoying enough as it
is on NM, but a freaking BOSS ROGUE c'mon! He stealth like crazy and
if Avaline is not on 70%+ she'll get oneshottet, and to add salt to the injury
he is nearly 100% immune to every bloody CC I throw at him.
How the **** did you beat him on NM?
BTW I’m a lvl 13 mage waiting to get BM, and my party consists of Avaline,
Anders and Varic ofc.
He's not that tough. His main weakness is he's bound to his room as long as he's not actively engaging a party member. Your Varric has Stealth, I assume. What you need to do is to trigger the battle with Varric only: the rest of the party should be put on 'hold position' as far from Bartrand's room as possible (preferably, behind a closed door). Now, run with Varric into Bartrand's room and stealth. He will eventually come out of stealth and go back to his natural position. Unstealth, kite and shoot. Bartrand won't go back into Stealth as long as you are close to his natural spawn position. Don't worry, the guards won't rush in to help him -- they won't perceive you at all. He'll just try to AA you to death, and kiting him with a ranged character is really a piece of cake.
Alternatively, you may want to: (a) trigger the ambush, let Bart stealth, stealth with Varric, then run out of Bartrand's room downstairs and leave the main hall (get as far as possible); (

wait a bit, let Bart go back to his room (he
must do it, if no one is in his limited perception range); © engage the ambushing guards with your whole party -- Bart won't get aggro on you, provided you are careful enough (his room is upstairs and quite isolated, so there is little chance you will provoke him). After the minions are taken care of, keep Bart unstealthed with Varric using the method I described, but now you'll have your whole party with you to shorten the battle.