Welcome to Librarium Online!
Wondering what your opinion is this is my first time as Eldar
x14 Guardians w/brightlance
Warlock w/singing spear,the cover save power forget its name
X3 Hvy. Support
x5 Dark Reapers w/Exarch, missle launcher, fast shot
Autarchw/jet bike ,star lance,mandiblasters
The plan is to sit back and shoot with the guardians in front of the dark reapers and the autarchs to counter charge or hunt down the ocasiaonal carnifax, wraithlord, daemon prince or vulnerable squad.
I don't think you will win very often with this list, if ever. Your Reapers even with cover save will go down fast, and your Guardians will follow suit quickly after that. You really lack in any form of staying power. I think you will get run over quickly and without much effort.
Eldar in general rely on mobility and specialization to win, and you lack both. I suggest you have a look at other lists in this section of the forum and see how they are built and what tactics they employ.