The Tigers have improved no doubt, but their no better than any other team making up the numbers in the 8, IMO there are 3 groups in the 8 ATM (come seasons end), the ones to beat (Hawks-Cats-Swans), teams with potential to compete (Pies-WC-Freo-Crows) and the number maker upeters (North-Tigers-Bombers)
I'd be inclined to say that the Cats aren't quite on the level of Sydney and Hawthorn. They've certainly impressed early, but if it weren't for their experience and knack for winning tight contests, they could well be 0-3. That's not to say they haven't earned all three victories, because they have, but they haven't blown anyone away.
The Tigers and Bombers are probably ahead of North too, and both sides can probably beat anyone on their day, but I wouldn't back them to make the top 4... and are no chance for the flag if they don't.