First of all it's retardedly random. You can go and git sawed by the first boss even on Human. Not to mention Primarque(Primarque? English, motherfucker, do you speak it? You sure?), where your 40 hp is basically 2HKO, especially by boss Ranko. Although he might do it with just one, without artificer armour.
Different action options doesn't matter little. You just stomp forward and wrrrr everyone. Cover doesn't seem to work. You'll get hit in close combat afterwards anyway. Ranged option has uses only when get access to flamethrower.
Next, the gameplay is basically loot all the bosses and try not to die in the process. Last ones are actually unbeatable without a proper gear, which forces you to run to get them all fast before terminator appear. You get to loot a plasma pistol from a security, who stated to have a bolt pistol.
The plot holes come out. It's rather retarded to send someone practically in their underpance by marine standarts to kill the whole base and terminator, techmarine with their armor just by bolter@chainsword. The idea of looting seem reasonable in some other universe, where donning an armour does not take half-an-hour for a basic model. For a mission that seem time-critical. In theory anyway.
Graphically it's again just a randomized collection of images. You didn't even bother to use related ones. Flail-wielding terminator with thunder hammer, Imperial Fists apothecary for a techmarine, guardsman for a sarge(security officer), inquisitor for a librarian. Raven guard marines for common marines.
Well. I'd say you weren't trying hard enough, really.