Just to throw my opinion out there:

I find the notion of a dom having multiple subs a bit unsettling. It would be my estimation that most doms would not be willing to share their subs. It is this greediness that shows how hypocritical the notion of multiple subs are. I don't mean to suggest that there aren't doms that are willing to share subs, just saying that from what I've seen, it isn't the case usually.

As for your individual case, I would say that is out of line and you need to have a discussion about it. No matter what degree of control you give up, you're still a person and your concerns matter. I seriously question anyone who would try to quell that notion.

Best of luck with this!