I've used a Warlock, Wizard, and Fighter.
The wizard one was even worse, since it's my first playthrough, and I didn't even get to stealth attack them.
But, none encounters a problem when soloing them.

I didn't play Divinity, but I'm using my approach from some DnD campaigns I played or DM'd in the past.
I kite them, kill the one closest to me first using ranged option.

I used sleep with my Wizard.