The Warchief's Council Room is another confusing muddle of an encounter.
The squares marked "T" are a trap. When the trap is sprung, a portcullis drops into place ahead of the party - that is, stopping them from entering this area. An alarm also sounds in the rooms behind the portcullis, alerting the hobgoblins within.
The first observation to make is that, as written, the hobgoblins have no way of lifting their own portcullis other than breaking it down. Theoretically PCs triggering the trap can happily walk off again, content that they've locked the hobgoblins into their own rooms. But let's assume there's some hidden mechanism the hobs know about that's not noted in the encounter.
The portcullis is a waste of space. The hobs inside don't have any archers. It's not like they can snipe at the PCs as they try to break down the grate. In fact, if they emerge from their rooms at all prior to the portcullis being broken, they risk being picked off by ranged attacks from the PC.
So the room ends up being a straight fight, with an annoying delay at the start. It's almost identical to the Hobgoblin Barracks, with the Warcaster replaced by a Warchief. The Warchief is pretty nasty in this kind of enclosed space, as he has a rechargable burst attack that shifts all his allies up to three squares, and when he hits with an attack he offers all his allies +2 to hit that target until the end of his next turn.
It's hard not to think that the trap was intended to be on the other side of the gate, sealing the PCs in once they trigger it, rather than locking them out. With no avenue of escape, and possibly some players caught outside the portcullis, this would be a much more interesting (and lethal) battle.