"Flight to Salvation" - "Summoning the Dragon" [Campaign 4, Mission 3]

So, if we only have 1 stack of creatures, does the "Dominate" spell not work on them? Why is it that when the AI has only one stack, the "Dominate" spell works perfectly?

The issue isn't that we have only 1 unit (or stack, to use the proper term) – it's that after casting "Vampirism" on the Kshatriyas, they become undead, which has several consequences, and it will be impossible to dominate them without Sandro's cloak (Biara has this cloak in the final mission, so you need to be careful with her).