In terms of advanced stats, I think the closest we have to that is WPA (win probability added), where the Jays' bullpen is 21st at -0.07. We are also 21st in RE24 http://www.fangraphs.com/library/misc/re24/
Basically, the BP has been bad when you consider context. All in all, we've probably had an average bullpen with above average contribution from the parts that pitchers can control, but below average production considering leverage i.e. one too many key hits given up in high leverage spots.