Currently speaking a tank has no valid way of actually countering infantry, but infantry can use the anti tank rifle to poke holes in tank and more often than not breach and as such either anti tank rifles should be removed as they were before as most people didn't care and generally thought it was a bad addition considering how fragile tanks are. Or there should be some way for tanks to atleast take down one person. Now you might say just make your entire bridge cockpit whatever terra, except now you can't fully armor your cannons nor redstone in most cases, while it may be possible if you were to use a 600 block sized tank its not possible for a smaller tank. And now someone might say why not just build a 600 block tank and that would be because a 600 block tank would be large and incredibly difficult to maneuver in most locations with any sort of trees or damaged terrain which is incredibly common at sieges.