Yeah fire over your guys into enemies and you'll do at least as much harm to yourself.

If you scuttle around the flank and shoot 'em in the butt, the casualties for you should be lighter, much lighter, unless you're using a seige engine.

I'm not a great fan of that though. Is it not very realistic to flank with archers/slingers and shoot 'em in the butt?

I think its alright to line up missile troops behind the enemy line for the post-break duck shoot. Also I'm very happy to run javelin-armed boys around the flanks, let 'em fling a volley into the rear of an engaged enemy unit and then close for the kill.