Whirling Zap-O-Matic needs an actual cast-time for its two-hit kill ability. There does not seem to be any way to SEE the attack. There is no beam, spark, or cast that the enemy does. Melee results in instant death as a rogue. Throwing daggers while staying at range takes forever and STILL kills you in two hits. Hunters, mages, and warlocks destroyed it instantly with no problem.
I guess Blizzard allowed that enemy to be broken against melee for some idiotic reason.