This is one of those chapters Thracia 776 has that's so awesome I played it several times before moving on to the next.
When heading directly south, Karin can fly over the mountains and distract Shiva. She usually has to take another merc or two along with Shiva, but with her ludicrous Spd/Lck, she has no problem surviving a turn or two, by which time Fin and Safy will be ready to draw their attention. There's also a convenient chokepoint if you just want to stall until Fin arrives.
When going west through the mountains, it's about killing the brigands as fast as humanly possible (asvel, brave sword, etc) so you can stay ahead of Meteor, and/or getting Fin/Shiva to the exit quickly. I actually left the archer and thief alive for quite a while because they don't block the path forward. Dashin needs Karin to rescue him at some point, since he can't even cross the mountains.