Playing with people who know how to actually stick together and coordinate tasks are a lot more fun to play with on both ends.
I'm pretty sure it should be common knowledge to some people how tactical gameplay stuff works.
I mean, obviously medics are gonna want to stick close to people and heal them, snipers will want to stay back, engineers are gonna want to keep a look at their buildings (well, some people should know that)
and spies.. well at least be glad your buildings won't go down as fast :P
AND PLUS, there's training mode right?