There is no reason to stack until after the heart phase. I let the group decide which way they want to run and then I use the other side for flank attacks. After heart you need to watch your positioning with double plumes and bombs/landslide. People that say you have to stack are either bad or watched mr happy and think its impossible to do the fight any other way.

Warriors that say they do OMG DMG are also OMG liars... and there is a lot of them around. If you are getting beat by warriors you are either really out geared or doing something wrong.