Hey, try these strats. They work best for me even if I'm by myself. Round 1: Stay in covered area that is in between entrance door and back left corner of map. It provides best cover when clearing ads. Clear each set of ads (use heavy machine for the two witches that spawn each time so you don't get overrun). Go to back left corner in between ad spawns to bring down boss. I found sitting as far back as possible on the left hand platform (when you are facing that corner) the best as his fire rarely reaches that far back on the platform. Just make sure you book it back to cover each time reinforcements spawn in. Round 2: There is reasonable cover on the roof of the building at back right of map. Start there and focus on first round of ads, not Psions or boss. Once cleared, kill each Psion in turn without damaging the boss in between because you might trigger reinforcements. Once all Psions are dead, damage boss until reinforcements come out, clear ads and repeat. The main thing to watch is the boss trying to stomp your head. Just keep a close eye on the radar. Round 3: Go immediately to far left corner of map which provides the best cover. Clear ads first (you should have good cover from Hobgoblins here). Once all ads are clear focus on boss until next wave of reinforcements. The hardest part of this round is keeping an eye out for the Snap, Crackle and Pop crap that appears above your head and moving out of the way until it's gone. Hope this helps.