When I entered the room, I killed a single level 18 (as it says above), but after that (dunno if I triggered a chain, or if someone else just killed the spawn before I got there), with like 1-2 minutes in between them, 3 level 19 groups spawned, all of them with 1 Blightfang Broodtender and 4 'minor mobs', but they were level 19 as well.
They were easy as hell though, I was at full health after every fight (I'm level 23, so they were green to me).'
My 2 cp's :)