That's assuming said tank is using a conventional main weapon and remains within the strict tactical parameters modern MBTs do. 

Even today, the role of armor is changing, with tanks becoming smaller, lighter and more durable as compared to their WWII and early Cold War-era counterparts.

If I were to make a competitive high-tier tank, it would be the size of a tankette (http://en.wikipedia.org/wiki/Tankette), sport a turreted beam weapon, possess a plasma shield that can function as an alternative deterrent against melee users, and it would handle like a sports car (much like the M18 Hellcat and/or the Riptide All Terrain Vehicle). Add in some more defensive and offensive capabilities and you now have an armored vehicle worthy of the competition it's slated for. 

If mechs (which are inferior war machines when compared to tanks) can remain competitive in a world of magical swordsmen and quasi-magical cyborgs, a small treaded vehicle can as well. Their weakness against attack helicopters and infantry huddled within buildings don't apply here, since the tank's capabilities would adhere to the tier system set by Skall and not arbitrary limitations set by the independent assumptions and beliefs held by other players.