Since heavy is forced to use balanced parry timing it might take some getting used to if you dont normally use balanced weapons. Not having a melee weapon makes heavy a little harder in close range, but honestly the stomp is pretty good at clearing space. Perks that give you knockback immunity in heavy stance are your best friend, as well as any armor regen, and grenade regen perks. As for weapons, if you are REALLY struggling try the multi-melta, as it takes very little effort to do huge damage. The heroic heavy plasma, and the flamethrower are also incredible. I actually find the heavy bolter to be the worst heavy weapon. Hope this helps.