Ok, srs post tiem.
Heavy
The heavy is a complicated, yet simple class. Complicated as in spy checking, knowing when to run away, protecting you're medic, watching for snipers, knowing where all the nearest ammopacks are, and knowing when to hit the uber. Simple as in two weapons, point and shoot, you could call the heavy a true W+M1 class. For what he lacks in motibility and ranged firepower he makes up in health and CQC. Having a large hitbox is a major weakness to the heavy especially since its paired up with being slow as fuck. The other classes have big advantages over him, such as instakills, and high burst damage classes. Also, the very large cone of the minigun makes the heavy ONLY effective at close to medium range.
I'll update this post in a bit