I can only say they are not too strong.
They are too strong if you have too many, what I had call: "misfortune points"
° bad placing of characters
° not being fresh & recovered
° not having the EA's maxlevel
° not being empowered by the well in front of the Hag's house in the swamp
° not having cast HP extension by a cleric beforehand
Do all that and maybe throw a few black powder kegs in an open fire surrounded by enemys and the Githyanki can go and eat sh°°.