You really should change the shooting ranges of attacking units. I'm currently experiencing an infinite loop, two garde units shooting at earthwork walls from a range where grenardiers can't reach them. The earthworks seem to heal and the gardes keep shooting. I have to restart the level after reaching wave 30…
Longest game I had was with a duelist. I had the luck to get a MK-3 Revolver early, with an auto reload mod level 2.
It's still better to get a laser gun, but meh