So, I look at the sacrifice of the seven as an exchange: a life for a life.

I'm a bit late replying to this, but ijust finished the game and started reading a lot of discussions to think about a lot of the game's unanswered parts.

The 7 actually... add up; there's you, tealor and coarek as the big players. Together with your two companions, that's five. Then there's strong implications that nailaq/tharael (tharael woke up in a corpse pit, lives only for revenge, nailaq "shed his skin", knows you're "special" and lives only to suffer).

Though considering the latter two were not directly related to the main quest, unless the father's immortality attempt somehow tied into the cycle in an unseen way, it would be odd for the veiled woman to "waste" two fleshless for "unimportant" purpose.