For corridors, I think:
Throg and Ty (both have great melee damage and good defense)
Revaethan and Dorgath (the next best with great melee damage and good defense)
Tomas (needs to be protected!)
Carrow and Kelgar (the lowest melee damage (aside from Tomas) and okay defense, enough to help out in case attacked from the rear, and Carrow has good ranged attack for the front)
For larger chambers, I think to just combine the first two ranks and the last two ranks.
Throg and Ty (both have great melee damage and good defense)
Revaethan and Dorgath (the next best with great melee damage and good defense)
Tomas (needs to be protected!)
Carrow and Kelgar (the lowest melee damage (aside from Tomas) and okay defense, enough to help out in case attacked from the rear, and Carrow has good ranged attack for the front)
For larger chambers, I think to just combine the first two ranks and the last two ranks.