Was goofing around with wiz/chanter combo. Both are snare/rootable. Guardian does NOT summon and hits for about 750 max. Vorsirus summons and hits for about 1200 max.
Duo'd him and his guard with a SK and druid. Snared named, brought pet guard to our camp and got a head start killing him. When named arrived, cast aoe taunts to keep named on me (sk) while continuing to burn pet guard down. Once pet guard was dead, we killed named.
We spent at a few hours waiting on him before he finally spawned. He was at loc. -1130, -1300 when I pulled him, behind a rock if you are pulling from Verg zone. He didn't seem to have a Placeholder, so thinking he is a timed spawn. It was 7PM game time when pulled. Not sure if he wanders, we spent so much time waiting for him, I pulled it as soon as I saw him.
Does not seem to be related to the Guardian of the Mines spawn, as indicated in quest listing. Guardian spawned only a few minutes after Vorsirus was killed. Hope this helps a little.
He behaves like a pet, but spawns independently of Vosirus himself. When Vosirus isn't up, he wanders in a random-walk pattern just as he would if Vosirus was around.
If Vorsirus is up, the Guardian of the Mines will assign itself as a pet to him. If Vorsirius isn't up, then the Guardian is a standard NPC without the pet flag.
Easy way to verify this it to use '/pet leader', while the Guardian is targeted, in both situations.