Ditto, tried to clear this dungeon last night, guys never showed up, even tried the usual relog dance a few times. Killed his buddy down the hall to see if that changed anything, but no dice.
Still bugged as of 4-12, 3 AM EST. Sat in area for 3 30min intervals no spawn. Started counting people as they ran around trying to complete it and got to 78 and I finely logged out again.
The other Nord boss in his room has been spawning in at least one instance, and someone says she has to be alive for the captain to spawn, but some guy keeps killing her. Not sure if it's true or not, but I've gone through two instances now with no captain spawning either way.
Just to add my two cents, while I was questing there and came across this quest I noticed it was bugged too. I'm 45 now and stuck in Reaper's March on the main quest line.
This particular quest involving Captain Siro has been broken for at least 1 1/2 weeks from when I first encountered it.
Been a LONG TIME and still no fixes to the quests..
I killed him! Camped for about 20min then logged off for about 10. When I logged on a group was killing him and his buddy. I got a couple of hits in before he dropped.