On expert, my main damage dealers are overload and sentries, and sentries are only for when I feel lazy. Since overload doesn't take stealth actions, you can maximize its damage by boosting your damage reduction so that you only take 2.5% of your overload damage, then boosting your regen so you can do it 8-10 times before needing to retreat to heal. With a pillar to run around, or even just a corner, you can often kill mid-high health bots without using any ammo. It's also very helpful for dealing with bomb/shield/emp/radar bots because you're immune to the bomb bot's explosion, it works while EMP'd, and you can take as long as you want to blow up/regen/repeat.
