I found the gith'yanki patrol. Tried to fight them thrice now, but no fight lasted longer than 3 turns. I admit, I quit the last one before everyone was dead, as defeat was inevitable.
Battle starts and L4 Shadowheart casts L2 guiding bolt from a height position with 75% hit chance. Miss.
Then it's a gith'anky's turn. Attacks my L4 dwarf cleric, with 18 base AC and bless cast. She takes 2 hits and she's down.
After 3 turns, the L4 party's dead and the Githyanki have suffered quasi only magic missle damage.
(Lae'zel is L4 Battle Master with STR 18 and has Tyr's sword, but couldn't make more than a scratch before we were all dead.)
These dice roll misses against this kind of enemy makes for very short battles.
I talked my way past through them now.
DnD rules; and especially Larian's version of them; are very responsive to using every advantage you have.
Potion of Hill Giant Strength will give Lae'zel +5 to attack and damage rolls for an entire day.
A Potion of Speed will give her 2 attacks per round at level 4 (3 will Great Weapon Master) and potentially SIX attacks per round at level 5 which is the level of the Gith Patrol.
A scroll of Mirror Image will set your Cleric's AC from 18 to 27.
Faerie Fire will give your whole party Advantage on attack rolls for as long as you can maintain concentration with it. So will attacking from a hidden position.
Certain spells have unavoidable damage components, or will remove someone from a fight altogether until you get round to them.
Void Bulbs will group them up for between cleave attacks.
Finally, release will have difficulty settings that will mitigate some of the harsher mechanics if you don't want to engage with every tool at your disposal.