Maybe it would help if you saw myself or other streamers getting through those areas to learn some more tactics, but it's quite rare to die to it once you have the tactics down, regardless of how often it occurs.
For one, go in prepared. There's pretty much always a Grenade Launcher to be found before you even enter the Mines, and if you have one (or one of the other early-game launchers), then they don't stand a chance against you. In that sense the Mines are very similar to any Caves--enter one unprepared and your chances of survival can be significantly lower.
That said, it's still not that bad and a launcher is great insurance but still not required, because you can play the response squad against the Assembled if necessary, also using audio cues to find out where the fighting is and try to avoid it if you want.
If you want to even fight them with conventional weapons, that works, too, just as per standard tactics don't fight too many at once. Assembled have extremely high core exposure for combat bots, and two hits from any weapon in the early game will destroy one. And of course be aware of the layout so that Demolishers don't get the drop on you (again, I like to avoid the demos and let them take out the Assembled if possible, but others have different strategies).
I agree the Infestation can be challenging depending on where it happens, but it's balanced with the rest of the game, otherwise high-level players would be dying to it as well (but you'll see a ton of runs pathing through Exiles without issue).
I even later added a decent chance that you get Derelict assistance when fighting against the Assembled (which you can choose to just use as cover and run away!), so it's become easier than it used to be.
But over the years I've seen plenty of crazy screenshots--like try getting ambushed by a full group of assembled as soon as you drop into the Mines (without a launcher, even!), but they survived all the same...
Note that scenario (getting ambushed right away) won't happen if you change the difficulty level to Explorer, so consider doing that, or Adventurer, if you need the boost, but the default difficulty has been tightly balanced over years and is actually a little easier than I'd like it at the moment, so there won't be any changes there. The Assembled and other nasty things that can happen to you in branches are meant as a deterrent for the unprepared--branches are more dangerous than the main complex, stay out if not ready for them.
If you're dying that many times in a row (or really even just a
few times in a row that early!), you could probably use some strategy and tactical assistance and dropping screenshots on the
Discord can get you real-time help if you need it!