I just gave up on my latest campaign when it went from a mostly successful contract to a "base attack" by massive forces against my light 'Mech lance (my lance of light vehicles failed their support roll). I had the support of roughly two lances of allied and civilian light/medium 'Mechs, vehicles, and gun emplacements, but the opposition was mostly heavy 'Mechs, and included a Stalker and an Orion. Sorry, but when my side is outnumbered 3:2 (with me controlling less than half of it), averages about half their tonnage, and my pilots and vehicle crews are at a lower average skill level (mine are a mix of Green/Regular, theirs are mostly Veteran in a supposedly "Green" force), it's just not a playable mission. You don't take on a Stalker, Orion, Rifleman, and Dragon with an already damaged Phoenix Hawk, Firestarter, Locust, and Stinger, and still have enough left to deal with the remaining enemy Lights and Mediums. My ally's weak units seem to get chewed up and spit out one at a time in senseless single attacks against a mob, doing practically no damage in return. Result: automatic contract loss after about a dozen totally one-sided and badly failed attempts to get through it.
Looking at the force makeup, it appears likely to be a "nearly worst case" set of rolls, where my Light unit probably generated a "Medium" lance in opposition, which in this case ended up as something like a mix of Light, 2 Mediums, and Heavy, plus a vehicle lance, and the opponent then got a reinforcement group that qualified as Heavy, with a Medium, 2 Heavies, and an Assault. Their BV is just over double the combined BVs of the defenders, since the defending allies ended up being generated as a mostly worthless pile of trash, especially in the unimaginative hands of the AI.
Note that if the player fields a lance with 4 high-end units in a weight class, it counts as the next higher weight class (3 Jenners and a Spider would count as a "Medium" lance, without having a single Medium 'Mech), yet the AI can potentially field a unit with only one unit in its weight class and the 3 others in the next higher class (a Jenner, Wolverine, Dervish, and Griffin could be considered "Light"). The AI can also randomly field either that same class or one weight class higher, and may end up with reinforcements. That adds up to a case such as your 130 tons or less of 'Mechs up against up to 290 tons of opposition, PLUS reinforcements. If you're not at the top end of your weight allowance, and slip into the low end of the next bracket, it's worse. It's potentially stacked up to way beyond 3:1 tonnage odds against the player (possibly 5:1 or 10:1 if the reinforcements end up heavier than the original force), which far more than counterbalances the inability of the AI to win an even battle.
The AtB idea is great, but the implementation leaves something to be desired. I like a bit of randomness and odds that can vary from slightly in my favor to somewhat against, but not turkey-shoots for either side. In warfare, if you can't field a force at least theoretically capable of winning, you avoid battle until you can engage on more even terms, or else surrender, because you're just throwing lives away for nothing. Few historical battles were "balanced", but few were absolutely one-sided unless the one force was trapped or otherwise had no alternative but to engage. The advantage of a lighter and faster force is that they're difficult for a superior opponent to force them to fight. Unfortunately, the current rules leave far too many cases where you simply have to say "no" and suffer the "breach of contract", where no realistic employer (the DCMS might not be all that realistic about it) would demand that you send your light recon force to die in a suicidal slaughter against heavier units with no hope of victory.
