Actually did the spider fight without using explodables and surface abuse ( Didn't even knock it down shooting all the webs ). It's not tailored to beat it with any class atm ( Specially Melee ), the dmg it does is dumb ( Has heavy damage area attack ) just like the HP scaling and has infinite teleports. The only way you can beat it is through hide cheese. Also check how many spiders they throw at you at the same time. Even the small ones do good damage, it was so stupid xd. They literally want you to play like Divinity for the majority of encounters then some kid comes out and says: "You don't have to use the D:OS mechanics if you don't like them" haha. That is what "Balanced encounters around the D:OS System" does to a D&D game. That's why the 5E ruleset had set HP for monsters too because the AC system exists and now we have it all Larianized.
Same my dude... my 4'th playthrough, i use two rouge and most of the fight i had to stealth cheese the mechanic they have in BG3... The spider does beyond any phase spooder damg in PHB. Also beat her with the cheese where i keep throwing potion at one of my down rogue, while the other bonus backstab till the matriarch die. Now i see some people are saying they have to sell more copy that mean dumbing down the mechanic or LACK THEREOF of DnD 5e.... Knowing now that a company of 17ppl can recreate the 5E rule so well, almost 1:1 and works great, now there people are doing mental gymnastic to protect Larian who promised BG3 will "faithfully follow DnD 5e". Is astounding really...