I dunno, while those DBacks/non-DBacks numbers aren't necessarily meaningful, they do still show that a reliever's worst stretch of games can distort an entire season's numbers.
But mostly, relievers are so variable that it can go well just as easily as badly. There are a lot of older name brand guys I wouldn't have wanted to touch over the last three years who have actually been good. And a lot of bad ones too of course, many of them wearing a Phillies uniform.
Best case, he's Knebel 2.0 but hopefully bettter (and stays healthy). Worst case he's Familia 2.0. Best case, Cotham can actually do something with him. Worst case, he's another Castellanos (i.e. someone Dombrowski overrated and overpaid because of past history).
I do think this was a response to the Mets because if they'd wanted a $10 million+ reliever in general they should have done it when there were better ones available (and paid more). Now you've got a guy who might give you more than a Bellati or Familia type signing if he has a comeback; but is much harder to demote or release if he doesn't.
I do think they did probably need one more late inning arm though. Taking away innings from Seranthony and Alvarado is a feature not a bug. The money doesn't matter, if they need to spend at the deadline they will (and again, a response to the Mets). For now still probably better to spend it on a reliever than a spare-part hitter who wouldn't have a job in July.
I think they'll be happy to get 1.0 WAR from him for the money. The market's inflated. And you just shouldn't pay relievers (and proven closers) for WAR in the first place. He did pitch great for the Cubs in 2021. Of course he also pitched poorly for the White Sox in a non-closer role.