@Sulphurix_LXXIII don't mind the ones who run around looting so much. Everyone has a different way to play the game, I try and adapt my play towards their style. If they want to play aggressive I'll try and keep up. But there are times I won't push everything (typically I'm really low on ammo or heals).
If they don't want to play aggressively I'm cool with rotating and looting as we go. I would rather not put them into a position they can't handle. Then force them into a hot situation in which we will most certainly die.
The ones that bug me a bit are the people who steal loot from death boxes. I play by the revive, heal, loot. Kind of bothers me when I clutch a 1vs2 or 1vs3, revive the downed teammate and they run straight for the death boxes swiping everything good, while I either heal or revive our third.