Ballin was still in rehab at this point in the off season when he got here, and wasn't fit till about round 10\. McQueen is already back on the park and is expecting to get the green light for full contact in the next couple of weeks. Not really comparable.
What was McQueen's status when he actually signed with the Tigers?
Oh, and much as he says he's in full training:
"I get my six-month check-up on the 10th of January and hopefully I get the green light to be able to rip into everything. With the contact we're being overly cautious."
Yeah that sounds like he's totally good to go for 24 games next season. He had nerve damage and was getting burners every tackle, and six months after surgery he's still waiting for clearance to resume contact. If you think this guy isn't a massive risk to miss serious playing time you have your head in the clouds.
Once he gets the green light, I don't see what the issue is. As you said, he's had the surgery. It's taken 6 months, because he's had the luxury of the off season. Why rush it when he has time to ease back in? There has been no indication that he hasn't been on track for anything less than a full recovery. Don't let boogie man Ballin spook you.
The biggest predictive factor of future injury is past injury. The second biggest is age. McQueen has both, in a big way.
The mistake isn't signing a player because I think he's somehow the same as Matt Ballin. The mistake is signing an ageing player carrying a major, major injury. I'm not scared of the Ballin situation happening again, I'm saying there is far too high a chance of the Ballin situation happening again because the Tigers have made the exact same mistake: signing an ageing player who hasn't yet demonstrated he can come back from a serious injury he was carrying when he was signed. And for multiple years!
Look, it's possible that McQueen will play 20+ games every year of his contract. But it's much, much less likely than it ought to be based on the contract he's been given. He's a highly risky signing - and that's a fact.