DH and I sailed concierge last month on the Dream (4-night itinerary). What we ended up doing was looking at what DCL recommends for the other tipped positions on the ship and then arriving at an amount based on how much we used each person's services. Tips for the concierge hosts are divided evenly among the three-person team. DH and I decided on $15/person/day, or $120 total. We were regulars at the early cocktail reception and typically had two drinks apiece. We tipped the bartender $40 (cash). We stopped in the lounge at least twice per day for snacks, coffee, and bottled water, so we tipped the woman who was in charge of food and beverages $20 (also cash). We asked for two extra tip envelopes in the concierge lounge and used them for the bartender and the woman who took care of the food. We just crossed out "Server" and wrote the names of the people we were tipping.
I agree with you 100%. We tipped the bartender on the very first day during our meet and greet with concierge. We were taken good care of the entire cruise. I also think most people don't think of tipping the beverage/snack people. I also did this at the beginning and more during the cruise. I received from Bosco (India) on the Fantasy a huge fresh premium fruit plate and also a plate of desserts in my room every day. My friends in other concierge rooms did not get anything other than the 1st day fruit basket. Now I could have gone to the lounge to get some of these items but some of the fruits/desserts were not available in the lounge. So I feel I was treated extra special. Bosco even said when he Skyped his wife he told them about the nicest couple he had. Heck I thought he was very nice and would have loved to take him home with me.
I didn't use the concierge hosts that much, but they were able to cancel some tastings & reservations for me the day of without any hassle. Also I put in a special request that I really didn't think could be handled--but they did handle it. I was overly impressed and tipped accordingly. AND I was also told by Kamesha that they do not receive a salary--they work strictly for tips and all tips are split amongst them.