If you are valor rank lvl 65 and lose 1.3lvl if you leave then you will not do that more then ones. Simple you lose 2% first time you leave then 3%, 4% and so on, if you lose a game to fast same but there you start at 5% and the longer the game gose on you end up so you gain instead off lose valor.
If you lose enugh lvl you cant wear the Warhero gear / BM gear.