I need help with defeating Draconis. I’m not even close. This is my first playthrough, and I play on core rules and with the goal of beating the game without any party members dying at all. I’ve made it this far starting from BG1 and would very much not want to have anyone die to him or have to lower the difficulty now. Only, I’m out of ideas.

His human form is easy enough. I cast breach and attack him, he goes down fast, even with the tank fighting him alone. Then he turns into dragon form and I lose.

Here’s what I’ve tried so far:

• Attack with solo tank and cast breach and time stop to throw as many spells as I can at him. My tank gets somehow stuck and cannot move (or maybe Draconis casts some weakening spell) and often dies before the mage is even done casting time stop. The odd time I actually managed to cast time stop in time and cast comet and horrid wilting Draconis got down to low health and healed himself immediately after time stop ended.
• Gang up on him with everything I’ve got. Dumb idea, everyone dies rather quickly.
• Summon planetar, deva, whatever I can get. These summons die directly when he turns into a dragon and I don’t have time to cast a new summon spell before someone is already dead.
• Try to hide my party in a corner. Either I’m too late to do that and he kills someone, or the one time I managed he went after some stray summon, stumbled upon my party and killed everyone anyway.
• Try to cast breach and dispel magic and whatnot to debuff him while I attack, but he just casts everything again and kills my party no problem.

My tank has 50% acid resistance, it doesn’t help all that much. I use the silver sword in hopes of getting a vorpal kill, but it never happens, or flail of ages 4.

My character is a berserker at level 32, so in theory should be able to handle this, but can’t defeat the dragon anyway. Party composition: bhaalspawn, Imoen, Jaheira as healer, Sarevok, Aerie and either Neera, Nalia or Keldorn, depending on situation. All are between levels 18 and 27 at this point.

I’ve defeated the demogorgon in a few tries, but this is way harder than that for me. Any suggestions? Or should I just give up and lower the difficulty at this point?

UPDATE: I've finally managed! Draconis is dead and all party members are alive! What I did was to equip Shadow Dragon Scale and Helm of the Rock on my fighter for a total of 75% acid resistance from equipment. Then I cast acid resistance spell on the whole party. After that I cast all the buffs I could get, especially protection from fear and haste on everyone. Also summoned 2 Mordekainen's swords and a hakeashar.

When ready I attacked with my character, Sarevok and Jaheira in the front, and Imoen, Aerie and Neera casting spells from distance. Human form died almost immediately and when the dragon spawned, I kept fighting/distracting with my fighters, while the mages were all casting spells and removing protections from Draconis all the time in the back. Imoen managed to cast a time stop and throw some comets and summon a new hakeashar. That brought Draconis' health low. My fighter got stuck under the dragon, but with all the resistances and healing potions was doing okay for a while. Then Neera cast Abi-Dalzim's Horrid Wilting, and that ended the dragon. Victory achieved! I might note that I tried to cast feeblemind a few times, but it never succeeded.

Thank you all for your advice and suggestions! It did help me to optimize my approach. Now I may finally move on with the game! :)