Varian will stop at the end of the sewers, unwilling to progress and unresponsive to any amount of /say bruh
The issue I found was Jaina had not joined the battle. I had to exit back through the sewers, use the NPC to exit the phase and re-enter the phase. At that point Jaina was walking to Varian, when she arrived she commented on the stench and the event continued as normal.