Easy mistake to make;
IMO Matrix of Ruin is better, but it does require points be spent on more troops, and has neither allies nor fortifications (though I can't remember if onslaught does either :X)
EDIT:
As for the list itself, I think it's okay, if you believe you can endure almost never going first (the firepower of some Heresy armies is withering!). I am not sure exactly why it's Ordo Reductor, but that's fine. If you can find the
HQ slot somewhere (unlikely) bring a Macrotek to stuff in the Explorator - he repairs on a 3+ (with a Machinator Array), gets a re-roll (
IIRC!) and can repair twice (this one I am sure of). He only needs a bare minimum 85-point servo-arm automata squad to repair more than the squad you have already for considerably more points, as well as allowing you to bring the enginseers as troops and make them scoring.
In fact, if you can figure out how to add him in, you could use the Age of Darkness army list with what you've already got listed.