interresting... what is the significance of the battle leader? is he the one one-shotting the engis? Is he doing superior DPS, or is he ignoring pets?
Running as engineer, i've had my hacker one-shotted even with the corridor packed with turrets, mortars, generators and whatever... happened more than once...
I suppose that is a distinct possibility that the real crux of the problem is to keep the battle leader's aggro on yourself, and not on your engineer.
The fleet I run with already had terradome down to a science when I joined up... also was the first time i EVER got through that one small room with the 8 incubaters, without having a massive zerg-respawn-lather-rinse-repeat cycle (Edited this sentence for clarity)