I've been achievement hunting with Paragon lately (gotta get that Autocannon achievement), so I've experimented a lot with my hanger to try and get opponents that I can kill with that dumb Autocannon. I've noticed a few things.
First, if I add even a single legendary item (say an implant for instance), I will face opponents (bots or live, it doesn't matter) with multiple legendaries each. And I'm not talking sometime small, I'm talking a bastion or eclipse with discs, nearly maxed Stephania, and at least one legendary implant. I'm dead in like 2 hits. Not fun.
Second, my squad power matters, sort of. I've got my squad down to under 1000. I've only got two mechs, both common, using common weapon, rare pilots, and the best implants I've got for them. I can tell as soon as I see the mechs from my team if I'll live longer than 30 seconds in the match. Some matches I've got opponents that are level appropriate, some matches they blow me away so fast I want to break the keyboard.
Finally, if I do really well for a match or two, the game will hammer me for the next 3 or 4 matches. By really well, I'm talking me keeping Paragon alive for the whole match and getting 5 kills with the autocannon. But then, I'll get hammered by bots or live players with legendary this and that. even if I run a setup without any legendaries at all!!!
I do think the matchmaking has gotten better. but this feast or famine thing that's going on is not right. There should be limiters in the game somewhere to keep some of the things that are happening from happening. If I have a squad with only 1 legendary implant, none of my opponents should have more than one legendary implant. If I'm doing well with my squad, I don't want to get destroyed for several rounds. I don't mind it if my opponent uses good strategy and beats me, but beating me just because they have more legendaries or more upgrades than me should never be the reason they win - whether they are a bot or a human being.
Hopefully that all makes sense. if not, feel free to ask questions, I'll give the best answers I can.