for me this part of CoS is easy although I haven't done the timed version of it. I have a pally and 3-4 shaman (sometimes a druid )

I run past the first group in the Inn and setup just before the stairs ( their backs are to me ) and drop totems wait until they convert and then burn them down.
I don't loot, as soon as they are dead I run my team up the stairs past where the 2nd group spawns but before the hall way, re-drop totems.
when they spawn burn them down from there, they usually attack the NPC first.
I move my team next to the wall for the hallway (almost there already, very little movement) so I can LoS the 3rd spawn group there , I run my pally to where the first half spawns and drop a concecrate when they spawn ( near side of the hallway ).
I run about 1/2 way down the hall way with my pally and avenging shield the second half of the group.
run back to where I have my team and they clump up around this corner to the hallway very nicely.
as soon as they are dead run down the hallway and setup for the last group and the boss that follows them.

I used to panic and died several times then all of the sudden it was never a problem again...