There's nothing wrong with going the standard Mei/Water blitz team, it's pretty solid overall. you could always substitute Mei for Tobirama like I have, but I wouldn't recommend using both in one team since they both use 60 points of chakra for their mysteries. So unless you have your last character somehow recharge 40-60 points of chakra every turn it'll be difficult to use both Tobirama and Mei to their full extent. Hope this helped :)