Blackheifer would make some good points, if they didn't continually feel the need to dip the beginning and ends of their posts in back-handed insinuation, belittling tone and condescension, or personal boasting. Maybe lay off with that?
Answering the complaint that a particular fight is unbalanced and unfair without abusing Larian's abusable cheese mechanics, by listing a whole bunch of things that you should considering bringing to the fight with excessive meta-knowledge, or more of said cheap mechanics isn't really that helpful... it mostly just reaffirms the point being made.
1) The charm the beholder uses is a double-edged sword. It breaks on minor damage, so every time he releases one and you hit it there is a 50% chance they attack the beholder depending on who is closest. This further saturates the environment with targets for the beholder to go after besides yourself. It's sort of brilliant because its almost like the fight is designed to upend and randomize the action economy. You may own the action economy, or you may not.
This is a legitimate point - however it trades on the 'tactic' of "Hey, use YOUR turns to break charms and HOPE that you get LUCKY enough that the drow decide to attack the Spectator before you! (They might not, and even if they do they still consider you an enemy and will attack you during and after the fight with the spectator)"
2) The Explosive plants that are littered through the battle area can be used to; damage the drow to release them from the charm or damage the beholder who often moves itself into a position near one. Just shoot them.
This is saying: You don't NEED to use Larian's cheap cheesy things... you can just use the terrain that's littered with an excess of explodable objects! This is like arguing that you don't need to drink water - you can just drink the naturally occurring H2O instead.
3) There is a Spear you can find that deals additional damage to enemies with multiple eyes and has a chance to blind them. You may have found it by now if you dealt with the owlbear.
Legitimate point, although, I only tried using the spear on a spectator once or twice, and it truly didn't seem to have very much effect at all worth noting; blinding the spectator (when it worked) didn't really inhibit it much. It certainly didn't stop its eye rays. On a related point, I'm generally not a fan of "Here's this overtuned fight, but here is also a special magical maguffin that is only going to be useful in this fight that will make it better." It's a cheap, dull and utterly uninteresting story mechanic and even worse as a combat device.
4) This is a good battle to bring in the Ogres if you managed to convince or bribe them to allow you to call them into battle since they will fight on your side.
Which is equivalent to saying "The fight is not overpowered for the party or too hard - you just have to bring along something even more overpowered to beat it with!" That's not strategy, it's a cop out. It's an admission that the fight IS overtuned. Also, once again, it's relying on coming into the fight and situation with foreknowledge of it.
5) There is also the Spectator in a Bottle you can use for some funny spectator on spectator violence. of course you have to kill that spectator then as well. To be honest I only use this method if I want to randomize the action economy further and up the possible challenge level.
This one I did just for the fun of it... but in reality, both spectators treat you as an enemy, and are far more likely to target your party than each other.
6) This is one of those encounters you want to save potions of speed for as well as Hill Giant strength, void bulbs and other explosive items. Invisibility pots can give you an edge allowing your strongest fighter to get close (lae'zel), pop a speed pot use the wyvern poison and then go to town on the spectator.
This is equivalent to saying "The fight isn't overtuned, you just have to metagame the hell out of it by saving a bunch of specific items specifically to use for it!" Again, no, that doesn't fly.
7) Glut is also a huge help here, especially if you use him to Myconize a Deugar or a Minotaur. Duegar are easier to transplant.
This is the same as point 4, although I'll allow it a bit more leeway in terms of fairness, since Glut is more likely to be with you organically at this point, possibly. Unlikely still, considering but more likely than point 4.
Ultimately, they have not actually answered Ibrahim's question, either - they asked how they used the abilities of their party members intelligently to best the fight. None of THESE solutions have anything to do with using your actual party or their class abilities.... it's almost all external stuff that could be just as easily activated by moderately well-trained dog (#CompanionScratch):
1) Get other people to fight for you, you might get lucky!
2) Get other things to do damage for you, there's lots of them!
3) Use the maguffin that was conveniently designed for this fight!
4) Get another monster to fight for you, then kill it afterwards!
5) Get other monsters to fight for you!
6) Stockpile strong items (and explosives!) to use for this fight - like you know it's coming!
7) Get other monsters to fight for you!
NONE of those have anything to do with using your actual party and their actual class abilities strategically or intelligently.
If more than half of your suggestions involve getting other, stronger monsters to fight on your behalf, that rather sounds like a resounding admission that the fight is, in fact, overtuned.
