I can answer this question because I solo it all the time on hard. So you chill on the other side behind the lamp things next to the bridge. Chill on your left side one. From there pop in and out killing thrall etc. after a certain amount of kills the ogres spawn. I'm talking about 20 kills or so. So behind the lamp if you pop out to the left you will see the ogre in the back. The trick is to hit him twice with black hammer before he notices you to stagger him. And shot while he flinches in his crit so that as soon as he stops flinching he will flinch again. Second over your gonna jump up while still staying behind the rock and shoot gally at him. It takes less time than having a team build the bridge and wipe etc