If a character is not having your characters back even when just walking down the street, shopping, or sleeping( there is always someone on watch and you always share a single room when you sleep) then your not really a party working together, your people doing your own thing, which is what D&D is about. Sure a common goal, more likely a common threat may arise, a common adventure trigger, to make those players who are all playing adventurers band together, and may during the quests become a tight knit group. but they also may not, maybe the half orc truly hates his orckin heritage, but when he goes to aid the elven ranger who is dieing, finds that rangers last act is to take advantage of the auto coup de gras rule of surprise when attacked by a percieved ally. Maybe then that elf turns out to not be so fatally wounded, and took advantage of the chaos of battle to stick an arrow belonging to the enemy in that dead orcs wound to trick the rest of the party. The elf ofcourse has racial hatred for all orcs, and simply was biding his time for a moment to strike, he probably ahs no love for the rest of the party who are also all non elves. Hopefully when he is the last survivor, and the rest are rerolling, they are starting to see elves as the amazing race they are and making new toons of that race to avoid future issues. And since that elf player was using note passing constantly, no one would ever suspect many of those notes where plans being conveyed to the DM on how to kill off all the worthless non elves in the party.