There is a difference between hard encounters and running into 8 Power Armour Mk2 goons armed with gauss pistols straight out of Aroyo. If you need to metagame instead of reacting to win fights, the DM got it wrong. If he needs to put in unlimited ammo for the enemy while you have limited ammo in order to make the encounter "challenging", then you have a bad DM.
If we're still talking about the wererats, then it's not even close to the scenario you described.
Fuckers are off the beaten path, surrounded by high level traps. With "only skill user gets xp" on, my trickery dude got a whole level disarming them even if 2 exploded in his face. Rats aren't even that though, they may be hard to crack at level 3, but come back just a bit later and you mop the floor with them.
I agree that it takes a shitty DM to throw a lich at a level 1 party without any hints that you really shouldn't go in that cave, but fuck it, this ain't PnP, you can save and reload, hell, the fucking game even autosaves for you whenever you enter a new area. If you decided to play the game blind and iron man it to boot, then you're not
, just a moron.
If you want to bitch about ridiculous stats on monsters in this game, sure go ahead, fair game, but the fucking wererats in that goddamned cave are not the problem. In fact, this entire discussion is
. Back in my day, if some moron came bitching how some optional fight near the starting area kicked his ass hard and claimed it should not have been there or that he should've been able do it at level 1 with a stick, we would've labeled him a decline enabler and turned him into the village idiot.