2H Fury on alliance side is complete garbage in most situations, especially if your raid properly applies armor penetration debuffs. It can do well on Twin Emperors since the melee Emperor is immune to curse of recklessness and you can whirlwind neutral bugs for Bonereaver's Edge stacks. It's also decent in MC if you're tanking multiple boss mobs for infinite rage.
2H Fury on horde is a completely different story. You can easily do over 2k single target DPS with BRE on a short enough fight. DW will still beat out BRE on single target bosses with every armor debuff, though. If you're missing annihilator debuff, BRE will most likely do more than DW. 2H completely outclasses dual wield for any AoE fight/trash, however. You do not use slam on horde. I'd recommend staying DW spec and switching to BRE on trash pulls. With decent RNG, untamed blade + badge of the swarm guard single target can potentially beat out DW.
Arms will always do less than fury.