while testing Mictlan - bug or feature ?

[Pocus]

Tried thrice (first time while really playing, the 2 others just for testing), and in 10 turns, my starting level 2 priest never managed to raise the dominions above 3 in the capitol. And 3 was reached only once, and in the Last turn (the tenth)of the Last attempt.

He was auto-supplied with slaves (checked several time), and my max dominion was 6 or 7 depending of the test.

This is rather in contradiction with the rule about slave sacrifice which should generate a dominion roll equal to the max dominion level, if I recall well (so 60 or 70% chance of gaining a level each turn ??).

Can somebody knowledged in the dark arts of blood sacrifice clarify the issue?