Choose the route before the gate
Blackrock Depths has dozens of bosses and several routes. Arena, Angerforge/Golem/Incendius, bar, and emperor are different commitments. Agree on one route and stop point before entering.
Key route mechanics
Incendius route: fire elementals are immune to fire and hit hard. Confirm that damage plan before walking into the elementals to discover it.
Bar event: six waves of non-elite dwarves, then Plugger. Area damage helps. Without it, assign targets before the first wave.
Lyceum: mobs keep respawning while either torch remains unlit. Name the torch runners and move with purpose.
Emperor Dagran Thaurissan: he hits hard and Moira heals him. Interrupt Moira or settle in for a fight that has forgotten how to end.
Length and respawns: long breaks can mean refighting cleared rooms. Bring supplies and plan time for the route.
The route discipline
Set the wing, the stop point, and the condition for changing either. A full-group reroute is fine. Do not debate the route while the healer is drinking.
Route agreement
The dangerous BRD route is the one nobody agreed to take.