from what I've played, I've noticed that so long as you don't royally screw up and let a whole bunch of Vek (the enemies) spawn all at once, then there is always some way for your mecs to completely prevent any damage to the grid within any given turn, no matter what you have or where you're positioned.

perhaps i was just being optimistic or lucky, but it always looked like that no matter where i was or what i had, there was always some way to counter everything that was on screen, like the game took my position and abilities into account when moving the vek around. Often times i'd notice this when some Vek moved but didn't attack, like there had been some cap on attacking vek. of course this all goes out the window if you spend three turns moving vek around and blocking vek from emerging without actually killing anything, then letting all those blocked up vek emerge at once, but otherwise, yeah.

Granted i also used to believe that some server admin on Hypixel (the minecraft server) had secretly given me a very small buff to attack and armor because they liked my minecraft skin, thus explaining why i was "so good" at Blitz Survival for awhile. so i may just be superstitious