LoS Stategy
Before each wave of trash before Falric and Marwyn, everyone except the tank hides in the corner of the left alcove, out of the line of site of all mobs. The four players (healer and 3 DPS) stand on top of each other. The tank stands in the middle of the alcove in plain view.
When the mobs activate, the tank allows the melee mobs to reach him, and uses abilities (e.g., Thunder Clap) to aggro them. The ranged mobs may aggro on the tank immediately, or, having aggrod on a hidden party member, will have to run past the tank to reach their targets. In the latter case, the tank's close-range aggro abilities can be used to take aggro. In this way all of the mobs in the wave will be aggro'd onto the tank.
The tank then runs into the corner (where the other party members are hiding) to force the remaining ranged mobs to run to him. As soon as the tank reaches the corner (but not before), the other party members leave and spread out in the alcove. All mobs are within AoE range of the tank and the fight can proceed on the party's terms.
A similar tactic can be used while fleeing from the Lich King. There is a recess in front of each of the four ice walls raised by the Lich King. These can be used to force attackers into close range, if all party members cluster there as the attack begins.