I did my first playthrough with 2 Warlocks, a Wizard, and a Rogue, which is likely the worst possible setup imaginable considering the state of spellcasters right now, and I did well enough.
Manage your short rests and your long rests a bit better.
My opinion is that one of Larian's top priorities should be doing a better job of having the game teach you how to play well. What you're describing is currently far beyond my skill level and the skill level of a lot of players and the game does not do a good job of telling players what they need to know to be good at the game. It leaves a lot of stuff up to the player to figure out without guidance and when you're outnumbered in pretty much every fight, that's not a good thing. The game should not take for granted what the player will figure out and it absolutely needs to assume that a new player does not know D&D rules and systems. I only realized how important using the environment was here on the forums and I'm someone who has been playing cRPGs for close to a decade.