It kinda reminds me of Battle Isle: Incubation, of which i have fond memories. If they fixed some of the system weirdness (the better the weapon, the lower its accuraccy, wtf) and removed the card collecting crap, it would be even better.
I wonder how difficult it is to produce a small scale tactical game like this...
Incubation is a good comparion. It has some strong incubations vibes in the second part indeed.
Lower accuracy for higher tier weapon makes low tier weapons not utterly useless, as they work better with a newbie in training.
The card collecting can get nerve whacking indeed, but at least, it makes you have to adapt to whatever the RNG gives you.
My biggest problems are the animation speed (Marines are massive AND FAST. They should not crawl and inflict the player such pain when he is forced to spend 70% of his playing time watching them move ponderously from one tile to the next), and the AI freeze bug (sometimes, the AI freezes during its turn, and you have to abandon the mission to continue, resulting in a lot of lost XP).
The campaign structure is a bit like Diablo : You need to finish the game in normal (=easy) mode to access veteran difficulty with better rewards (you get 20 RP + 1 random item in normal, 30 RP + 1 random tiers 2+ item in veteran, and I suppose 40 RP + 1 random tiers 3+ item in hero), and then finish veteran to access heroic difficulty.
The problem is that normal is a bit too easy, but Veteran might be too hard if you were to start it without lots of unlocked stuff and good XP.
Overall, I am still having a good time with it, but it is not Chaos Gate (battlefields are much smaller, you have much less Marines, and death is not as sudden : your Marines can usually take a lot of punishment there, unless facing a Hive Tyrant or Carnifex).
I would definitely recommend it once the two issues I mentioned are fixed (animation speed and AI freeze bug).
It is more expensive than the iOS version, but is not plagued by its microtransaction galore (iOS version grants 4 times less req per mission)