XCOM: One Does Not Simply "Shoot" a Cryssalid...

[ShneekeyTheLost]

Mobility. In Ghost Armor, nobody can outrun these guys. They are perfect to act as scout or relief for squadmates down or likely to be the subject of heavy fires.

Assaults can sprint and shoot (Run n Gun), which gives them FAR more useful mobility.

Give them the Arc Thrower and they can probably get into melee range much more easily than anybody else. With 2-items, you can even have them keep their medpack.

Give your Arc Throwers to your Assaults, they're more likely to get up close and personal with the aliens, and more likely to survive the process.