Do not chase. Hold block. Let them exhaust their stamina on your guard. When they kick to break your guard, dodge backwards (using your 25 Agility Observation), then immediately use Glacial Arc . They will attempt to dash in. Hit them with Lumbering Slam . They die.
A Heavy build is only as good as its ability to ignore the opponent's puny attacks. Look for these: Exoskeleton: Massive physical armor boost. To the Finish: best heavy weapon build deepwoken