I have a rank 3s team that went platinum. We're having trouble with 3 people being online at the time and having team chemistry on a daily basis if you want in.
Long story short - we went Platinum mmr (like 40 LP a win but only Gold 2 at the time) and played Diamonds/Plats regularly last season. One day, the other two members had an argument and one of them left the team. We've been having trouble filling the gap for a while now. Nobody seems to have 3s experience so we've been sitting on the same team in Silver 2 with a good friend of ours, but a lower skillcap.