I've had a sniper shoot his buddy in the space next to him when he was clearly out of LOS from the alien I was aiming for a whopping 10 spaces away.
I can't count the number of times a grenadier has thrown a frag at his buddy a few spaces in front of him when the alien I'm trying to hit is 2x or more further away. And yes, they do tend to rack up ridiculous numbers of kills.
My usual loadout for a team of 12 consists of 2 snipers, 2 grenadier/medics (takes quite a while for them to get the strength to use the Jackal armor and the full compliment of nades and gear), and 8 assault troops. The usual arrangement is one cluster in the front with a sniper front center, grenadier/medic behind, and 4 assault filling the sides, then an identical group in the far back which makes use of the side doors.