Well, the first thing to remember is that no army consists of just one squad. Your melee troops will never get into assualt if they don;t have fire support taking out squadbusting guns, and other units providing a distraction. When I play marines,I have my LSTs buzzing the enrmy, raking them with withering fire and generally drawing a ton of fire while my assault squad leap frogs from cover toc over until they;re in range.
A skimmer transport means you can't completely hide behind it, but at least they'll have to make a Ld check to shoot your squad.
Try not to get too close when you deploy. Banshees are Fleet, which means they can move 6+1d6" and then assault 6" if you don't fire. Try placing your banshees out of rapid-fire range. They can close that gap pretty swiftly on your turn, and it;ll help keep them from getting mown down. If the enemy squad doesn;t have heavy weapons and isn't afraid to get in closer, you might place them further back than that, so they can;t move up and then rapid-fire your ass off.
Don't forget about terrain. See if you can deploy behind some piece of area terrain, or a LOS-blocking terrain feature, like a hill or wall. Even if it puts you a little further back, you can probably gamble on fleet to get you by.
Use the transport to harass the enemy. Tank shock them, shoot the crap out of them, keep it between them and you. aNything to make them focus shots on your serpent. Between the energy field and its fast skimmer status, that little monster is going to be hard to kill