I like the Miller deal, Yankees have stacks of cash to burn so securing a high end reliever for four years seems like a good investment. However, I think expecting Miller to regress vs righties is probably expected. I think with his frame, motion, and delivery he's going to be ridiculous against lefties. But allowing a .446opOPS vs righties (and he was almost as good the year before) seems almost impossible to repeat year after year. His career oppOPS vs righties was north of .875 after 2012 and now it's .787.
Not sure how many teams would have gone four years but for the Yankees it's only a bad move if Miller is a complete bust after say the first year. I think at worst he's an above average option over the course of that contract.