Warhorn is probably your best bet in PvP to counteract Axe's lack of mobility. Sword offhand works best in condition builds and while Mace offhand is strong, you're likely to get kited pretty easily unless you have fast hands and a more mobile weapon in your second set. Or one with more CC.
Melandru's runes are some of the most useful runes for a Warrior on any armor set, due to their synergy with -Condition Duration food and Dogged March to give you near immunity to movement impairing effects. I would strongly suggest working towards getting a full set of them.
Yeah the whole moving around thing comes from people who are inexperienced with dungeons. Most of the people who have been running them for a while now have stuck to that stack in a corner strategy (shame how low the dungeons have sunken that nearly every encounter plays out like that, but that isn't the players' fault).