Actualy deal as much dmg as possible is nice, you can see how much dmg you deal.
Me personaly, with a breacker-nova mech, average about 7-9k, in it.
The "god mode" challenge is also good, since you can see again the dmg output of your build.
The "invisi mech" yeah that is useless, it usualy pops up the shield and it generates a glow on the floor so you always know where it is. Also the wepons give way his position, in range/ out of range etc, and it's pretty easy to beat.