I completely agree with Timon. Playing medic in lobbies is very soul destroying sometimes. In certain games your team mates don't know what they are doing and this means you are dead as they don't protect you. Then if/when they overextend and die they go mad and shout abuse at you for not healing them.
The life of a medic is hard and ungrateful in many ways.
I think a guide is a great idea to start with. In general I think the community can help out all newbies, not only the medics. So if someone seems a bit clueless just teach them the right way. Ie, tell the new medic the heal order, the positioning and so on.
My first lobby was actually as medic in a 6v6 game. I had over 1500 hours at the game. but didnt know the heal order. The leader let me play (despite the whole team wanted to kick me) and he talked me through the heal order. We won that game. I was forever grateful to the leader who let me play the game.
I also think that treating lobbies as hardcore competative and putting 2000 hours needed is abit OTT and puts a lot of players of the game. I thought that tf2 center was kinda a stepping stone towards comp. A place where people could get a bit more feeling for the competative. And a place where the community could interest the newbies to play comp.
Obviously I do understand that sometimes you are fed up with the fail lobbies and so on. But give the newbies a chance to learn
Also people opening yet another lobby despite there being 5 hl lobbies and 4 6s lobbies open at the same time all looking for medics is not helping.