I honestly think that you gimped yourself with Arcane Trickster/Eldritch Knight.
Their magical capabilities are really not worth it.
I never died to the githyanki patrol, not even on the first try.
My party: Berserker (my friend), Bard (me), Wyll, Gale
I opened the combat being prebuffed with Haste by Gale. The patrol attacks first and they beat the Berserker hard, but they didn't down him.
After this, the berserker goes frenzy and goes to town on the patrol, we are all focusing on a single target at first.
We leave Baretha for last, because the other ones have lower HP but still deal quite a bit of damage.
I use my bard to put a Glyph of Warding (frost) under the patrol and I kill 1 of them, and seriously damage 2 others. I use my bonus action to heal the berserker.
I use Wyll to Hex the weakest survivor and blast her, she dies.
I use Gale to throw magic missile on the remaining enemies, focusing on the one with the lowest HP. Survives.
Enemy turn begins, one of them instantly dies after trying to move and Berserker hits with an opportunity attack.
Baretha tries to escape and climbs up the ladder. The berserker jumps after her and hits her hard with reckless attack and bonus attack.
My bard shoots the dual wileded crossbows and Wyll finishes the fight by hexing Baretha and elddritch blasting her.
Keep in mind that I could've used poisons and various other sources of damage on the berserker's weapons, but I didn't. We didn't dip it in fire either. I dont think using haste as a prebuff is cheese either.
This fight was honestly never hard for me.
On another playthrough, all I did was start the battle with a fireball from a light cleric and then managed to shoot them again as I was the first in initiative. 2/4 died instantly and the rest was easy to mop up.
