My friend showed me this yesterday when we were running ATR.
At the start of the map, have the warlock hellfire + health funnel pet. This will put the warlock in combat, and if you (healer, dps etc) buff or heal the pet, it'll put you in combat as well.
This will prevent you from getting sap as a healer, helped us many times against RMP and alot of times you'll be able to get the rogue out if they get too close to you trying to sap