NPC spawns should only contain 1 dmg type, and only mech types suitable fot the mech that they are designed for.
Currently my mech is sat in my hanger even though I can use it and have reasonable skills I can't hit anything with it because the devs went down the insane route of making cheap smaller mechs virtually immune to the really expensive mechs.
While smaller mechs should have a role it shouldn't be like this, a players expectation should be to grow into more powerful mechs, not be sat in a castel and thinking dinner time when they see a large mech comming over the hill.
Mission wise they are pointless over level 1 bar for standing, they take too long for the reward, and the mob makeup and their abilities puts them out of reach for many that play solo, and teamwise they would be pointless to do because of income.