Since now you can see who is in Squads with who's on your team, and if you really want your Team to Win, set your not full 2 or 3 person squad to Public, even if you expect friends to join later you can always change to a new Squad.
I've noticed that losing teams usually are not squad up and you try to get in to one of the 2 or 3 person squads and you can’t because they never set their squad for public.
There really is no need to be in a private squad on a rush or conquest match if you want your team to win.
don't you want to make it more possible to bring more players on your team to you and your squad when your in a battle?
team killing in hardcore is another topic... those teams that kill team mates are usually losing too. I kind of feel that this happens because players what the vehicles to use so more abilities on them can unlock, did not see that as much in BC2 but more so in BF3 since there is a lot more items to unlock now.
I think this squad issue is going to be fixed in the upcoming patch.