I find it slightly comical that devans posted his balance statistics on the table and yet people consider it OP.
1st of all, he has it right IMHO. Armagio protects from creatures, thus deserving 5 more health and +2 cost in comparison. This card could be easily avoided by a creature rush, and keep in mind that your PC cards will still work. (See #3 for comparison to Mirror Shield)
2nd of all, like doublecross said, AoE rips straight through this. If I interpret the card correctly every single effect casted by an AoE becomes redirected at storm rod. That means you only need a Plague or Retrovirus, and it's not exactly a good idea to run this in a deck focused on swarming unless you need AoE protection.
3rd of all, if this card is to be compared to Mirror Shield, then one could say it benefits from being a creature, thus having increased cost (as well as protecting from Poison, one thing Mirror Shield can't do). Protection from Poison and Multiple copies of a creature are enough for +2 in comparison to Mirror Shield.
It seems balanced to me. One question though - what happens when you have multiple Storm Rods out at the same time?