Here's my guide to survival. And domination!
MINER PROTECTION
This is simple, really, as I've noticed that they send melee units and ranged units to assault your miners, just send defenders and archers as soon as you see this and if you have any problems with that send in a cavalry unit.
DEFENDING ON THE ASSAULT
This is easier than Miner Protection, you just need to send defenders to take the arrows, then put archers following them, then put legionnaires to take the side enemies while a few healers are following. Then let some cavalry get to the battle to take the arrows with the defenders while your lesser troops dominate the castle.
DEFENSE WITH SMALL ARMY
If all you have is the ability to get three unit types, just get a defender, archers, and miners. Put some archers out there then some miners, then spawn a couple of defenders to go take them out, when your extra units show up, use them. You should survive the level.
Level 14 on alien campaign is something that cannot be completed honestly. And why does J.Rockit insta kill me with his katana and i don't? (same health/armor) - Noogai. The reason is because in the scripting Addison and Juice-Tin wanted the game to be difficult, so they scripted it to where J. Rockit does waaaay more damage than you.
What's so fun about jumping around destroying loads of other people on a massive killstreak with a laser rifle called a "Holy Grail" with unlimited ammo while your teammates are on Insane and your enemies on Very Easy so the game can be certainly dominated again? Oh that's the fun thing. Damn it is fun...
I could feel the curse, I was mutated... So as I drew my last Health Pack, there I waited ten seconds from utter destruction, J. Rockit, & Ex. Treem were dead, Md. Sage was my only man left, then I threw my mutated corpse in front of the bullet about to hit Sage, and it happened, I noticed I had a Holy Grail in my hands, so I blew his head off. And then we planted the artifacts.