If you play Lucio, its really hard to 'flash' skills that an algorithm can track. So placement matches are going to be a slog (real matches were mostly w/l). You have to show value over a generic average Lucio, and of course that's really difficult.
I only play Lucio if I know that i'm the least skilled player of the group, that way the best players can play carry heroes and you optimize your teams value.
People actually thought there was this thing called 'Elo hell' in season 1, which was complete bullshit. My guess is that this was mostly compromised of Lucio, Winston and Symmetra mains who were upset b/c it was hard for them to separate from the rest.
The right move of course is to play carry heroes (like Zenyatta if you want to play support) until you get close to your true value, and then you can go back to maining Lucio.