There is much difficulty in reviewing a lot of Warhammer40K games because while most of them are functional, polished as a product, and arguably loyal to the tabletop lore (let's not get into Codex wars though, I'm a filthy Chaos Marine) they somehow lack an extra spark of fun that would distinguish them among the mediocrity.
Don't get me wrong, I love Warhammer40K. The only reason I joined Steam, originally, was to play the Dawn of War series. I would be the first person to sing my praise to high heavens for an Orks (and Nids) Must Die! set in Warhammer40K universe.
As a software, it functions: it runs smoothly on my 4 year old potato, there is no glaring glitch or bug, and while some may complain about the obvious port it does not assign R2 button to your melee command so there's that.
The problem, again, is that infuriating question of fun and lack thereof. Considering this is not a lore-centric title with the sole purpose of slaying Orks, it fails to deliver anything but disappointment--I mean, I had absolutely no expectations and I was still let down. Camera seems to exist only to fuel your wrath, power-ups and perks are as stock as they can be (because of how bland they are, the super-serious announcement voice for power-ups is all the more cringe-inducing), and the sound effects seem to nag you with existential, self-doubting question: why the hell are you playing this game where guns don't even sound like guns?
The whole project, from the announcement voice to uninspired gameplay to its mini-game length, has something of a business-like air to it, like the game was not something the developers wanted to make but a soul-sapping obligation on their contract to churn out an action-oriented Warhammer40K game. As a fan of the series, its universe, factions and Emperor-knows-what-else, nothing is more disheartening than this.
Co-op will not change the lack of entertainment or soul in this game, so don't drag your friend or family into this. If you want a good co-op Ork-slaying experience, play Orcs Must Die 2.