For Destro, this guy "Master Moulder Vitchek" wanders around in the top of the Tunnel of Baradum in KV near 60k 37k. I couldnt find him so I went and killed the "Burrow Champion" Lev 38 champ. Master Moulder Vitchek is a lvl 19 Skaven Hero. I was surfing the web looking for him and when I alt-tabbed back to the game he was wacking on me. He was easy for my 40 HealDok to solo I just threw my melee gear on and he dropped like a $2 hooker.
I was standing on the bridge at the top of about 4 flights of stairs which mustve been in his wander path. Or maybe he spawned after I killed the Burrow Champ, I dunno.
He is coming randomly but i had do it in first time description is right.
Great, someone removed detailed info on Skaven Tactic.