Hi there! About the improving the weakness against CCs and Blitz .. In my opinion tho i'm not an expert with this so correct me guys if i'm wrong, just try to increase your initiative so you can move fast than your enemy, in that way, you can now have the advantage of the battle .. Then for replacing Water Main with other Main Classes, it is not advisable or good because Mei and Tenten gets additional power from Water Main's Water Enhancement Skill which you cannot get from other Main Classes, and if you do change class and Mei's barrier was overlapped by other Auto-barrier ninja, Tenten's and Mei's power will be not enough for battling .. For replacing Mabui, yes you can replace her but the essence of this team will be lost because Mabui is used as Chakra Feeder for Tenten, so that she can release her Bashosen - Five Elemental Rout in the first round, making you have the battle advantage .. So, improving Initiative and buffing up Mabui's Defense is the best way to have this team run smoothly and fine :D