My philosophy is to play pocket in proportion to the % of heals I'm getting. Medics love to play the victim and act like everything is everyone else's fault, but in reality they have a lot of personal responsibility with heal orders and priorities and such. I've played many 6s lobbies where the first round or two I play pocket the traditional way, meaning I'm right with the medic constantly and never jumping away. If I notice at the end of the first round or two that the demo is getting double the heals I am, I'm not getting flashed during ubers, and I'm never overhealed on mids or any time after, then I switch to gunboats and start roaming. It's more beneficial to the team to play this way when the medic isn't playing properly than to sit by him and just die because I'm not getting healed. If the medic questions why I'm not next to him and he's dying constantly to scouts and bombs, then I explain a bit about healing priorities and class roles. Usually they don't say anything though and the lobby continues. On a side note, there are certain maps where it's far better to have both soldiers play as roamers.
I have a big problem with medics that seem to think that as long as they are always healing something, they don't have to have any game sense, self awareness, or positioning. I feel this community as a whole coddles medics a bit too much, especially when far more often than not their deaths are due to their own bad positioning and lack of knowledge of proper medic movement in 6s.