Cruising Girl, I think the number of folks dedicated to concierge varies based on the ship size, guessing it varies because there are more concierge rooms on the Wish versus say the Magic. I believe I've read that there are 9 folks on Wish and 7 on Magic / Wonder but am unsure on Fantasy / Dream. Believe Magic Wonder are 3 hosts, 2 bar, 2 food?
Disney apparently has shared a recommended $8 / person per day that the concierge team splits based on pre-set percentages of the total. I saw on Facebook where someone had the break-down. I've seen and added the math before but was chastised by folks, but you can do the math by multiplying the number of concierge rooms (e.g. 44 on Magic) by a reasonable number of guests per room (likely 3-4) by the $8 / day and you'll see that it seems Disney set a good minimum target that if everyone in concierge paid the team would likely be taken care of beyond the salaries the hosts already receive.
I've seen some say they tip $30 / day per person and if you do the math there each person would potentially receive well over six figures in tips per year.
At the end of the day I think you have to tip what you think is reasonable based on your interactions with the concierge team. In the past when we've sailed concierge we didn't make much use of the team on board but still tipped closer to the range that Disney is recommending (again $8 / day / person). We interacted more with the bar team for 1-2 drinks each night versus the actual hosts.