I've just done it as combat, to passively cleave down adds. As for going sub, it just feels weird since you can use 2 min CD at the start of the fight, since they won't be up for when the robot dies, and that is when hero is popped so you lose out on a lot of dmg. But if you go combat you have more control over your CD's I found that I could use them twice, and still have them up for when the robot dies.