Bigfoots are tough creatures. They have a rock attack that will demolish most tanks in seconds, while having a claw attack for those high-dodge units. Either way, the bigfoots will destroy them without much difficulty. The 2.8 Patch has tweaked the bigfoots, making them far easier to defeat.
An effective way to kill bigfoots is to use splash damage. These include the Heavy Recon/Rocket Pod/Triple Strike, or any other checker/triple strike. It's also good to have units that have crit against critters, such as the Big Game Hunter. They have high dodge and defense, so the tanks would mainly be for defense purposes. This does not work against the player-trained bigfoots that will nullify explosive damage.