That's a good question Pyro, about the balrog. I never really was clear about the Balrog's relationship with the orcs. They weren't enemies, yet they weren't exactly pals, either. Maybe the Balrog told the orcs to leave the dwarves alone for awhile... doubtful though.
Let's see -- the dwarves did a fairly good job of wiping out a good portion of the orcs and they lost their troll as well (go Floi!). I do know that they flooded the gates of Hollin to keep them out (that's how Oin meets his fate...
) But what about the Great Gates? The dwarves will do repair work there. Maybe the orcs could tear it down again or whatever. So what the orcs could be doing was slowly sabatoging the mission from the first. Balin, in his stubborness, refuses to leave when given numerous chances to do so. Hence, the dwarve's final demise.
What do you think?
Cheers,
Imladris