My two cents:
I would not use a different number of doves per set (as I think it would lead to more inquiries at the help desk). So, I'd, say, have four doves per set and three sets total. Simply not too many because it can get easily confusing. Same with the colors. I personally would prefer each set having the same color or each dove of each set having the same color, i.e. the first dove of each set green, the second of each set blue... Genereally, I'm not too fond of too many colors, because there already are a few (mood button, membership band, color of the member's name, color of the title, the doves and the healing bar.
I think that the progression should be visible/noticeable in some way, i.e. by the doves' wings being more "in flight" as the doves progress (sorry, lack of English, hope it's clear enough) and by color, i.e. have the last dove be green because the healing bar is also green.