The Bieksa example was obviously an exaggeration, but I think the point still stands. So you're correct, if Bieksa turned in to some top pair guy, then he's probably not criticized for the move because the player justified the contract. However, I think it would be wrong to say that it was still a "good" signing when everyone knows it shouldn't have cost that much to sign him in the first place. I'm not saying your thinking is "wrong", I'm just saying it's easy to see why people wouldn't agree with it. Use this hypothetical scenario for example: Murray somehow manages to sign Tavares to a 1 year deal, 5 million contract this offseason. People would call in an incredible deal. Now, let's say that happens and for whatever reason (not injury related), JT has a god awful season. Say he puts up 5 goals and doesn't help with other intangibles. Would it be fair to say that Murray made a terrible decision? IMO, no. It seems like the logic you're applying would insinuate that it would be fair to call it bad because well, it ended up that way. I, personally, don't think it's fair to use that much hindsight when discussing it. The exception would be if you're paying for potential as part of it.
Now, I do agree that the Rowney signing is being blown out a bit. I think it's a really bad signing, but it isn't remotely back breaking or anything. I don't think my evaluation of him was pretty far off though. He's 29 and had one season where he played more than 40 NHL games. Prior to last season he played in the AHL primarily so I don't see how I'm pretty far off on my evaluation. As for what justifies his contract? If he plays and proves that he belongs in the lineup each night, that's probably pretty close. Doesn't change the fact that he hadn't done anything to warrant such a raise, let alone on a multi year deal though.