I think there is an element to who applies to go on to this program will dictate who the actual contestants are. It will attract a certain demographic...
I also think wes comes across as mature and measured for his age. I don't see any real idiocy there.
As for Rosie, I think we don't know if she chose to leave after qualification or if she was let go. She was a costing lawyer, so may have went the cilex route, ie only qualified to work in that one area.
I'm not sure, but it seemed she worked for a not very good firm, like a no win no fee scenario, and costing would make sense there (client/defendent liability) .
It's not really clear. She did say she got a training contract though, so she may well be fully qualified, she may also have left of her own violition to do this. She may be clever but she's clearly not smart.