Darren O'day is a decent pick up that is low cost and chance to right the ship. I fear that his role is so pigeon holed that it is not effective to have a guy who largely cannot subdue left handed hitters. Any typical bullpen should have right handed pitchers that have the ability to work an inning and left handed pitchers to be the LOOGY.
If you can get a LHP to work well against LHB and RHB, they are worth their weight in gold. Unless the RHP can be equally effective against LHB and RHB, they would not last long in a top notch bullpen.
He is worth taking the flyer, but I do not think he makes the opening day roster.