You take Seraphs with Enforcers, they have greater range. First Railgun Towers can be taken out by destroying barrels (with Sniper, he can). Later, you destroy Bio Chambers or just mass-rush towers with Enforcers.
But how do you stop those 4 chaos quads from destroying your entire force? :(
Okay so I just read through every page...basically I have to get lucky in what I get from the crates?