Actually, I don't think you need any specific class.
I play an Archer Artificer, but instead for single shot crit spamming from max range, I go full on melee. Hook & Tackle, Poison Cloud, Leaping Shot, Throwing Blades (all of which with the OP cooldown-reducing perk) ; a bow that gives me +7,5% damage per enemy surrounding me, and armor with 10% chance of casting Fade Cloak on hit. It's a lovely insane playstyle. I also go form over function for my entire party - I have access to better armor and upgrades for each party member which I don't use cause stuff half as powerful looks better. I also don't have a mage.
The only ones I have a hard time keeping alive is DD rogues and 2H warrior companions, though I probably would if I weren't too lazy to properly command them - and this goes for any difficulty. It's just terrible AI.
So what I'm saying is not "look at me", but you can make anything work. Use your tactics to always order the entire party to focus on each individual archer and mage & always let your tank storm in first, and everyone survives most encounters unscathed.
P.S.: Don't worry about the level. As far as I saw it, the enemies scaled to my level in both game states I entered the DLC.
P.P.S.: The fact that Blackwall eventually becomes virtually invincible also helps.