Purpose built Lokarr killer?

Since Malawiglenn pulled all his posts for some reason, I can’t recommend a specific build guide right now. But my approach for a Melee build would be to go with a class that already has natural synergy. Like Warlord or Witchblade with physical damage for example. You can make that work with Faction gear and target-farmable MIs, like Ugdenbog Girdle for Acid to Physical damage conversion (good Item for a Physical Witchblade).

Lokarr deals mostly Fire and Physical damage and reduces resistances by 40, so obviously you want to overcap fire resistance by at least 40% (you can use the fire res potion for the fight as well) and get some phys res going for you. Your Defensive Ability should be around 2700 because he’ll reduce it by 218, so he won’t crit you.

I’d probably go for Sword and Board to make use of Overguard to play it safe.

This Death Knight build should be a good starting point gear-wise. You can translate the gear for Warlord or Witchblade as well - or go with Death Knight.