As a feral tank - and really, as any tank would tell you if they were honest, Argent Defender is ridiculous. It's not just overpowered, it's superpowered. It's a relic from an older age when power just flowed like candy, and really shouldn't exist in this world of more realistic, 5% bonuses and gritty power benefits.
I mean, the guy can fly through space on a surf board. He is the herald of Galactus, who can eat whole worlds and has a weapon that erases you from existence. He uses the power cosmic - and that's like using cheat codes, basically. He's taken on the entire Fantastic Four and whooped them; the only reason they won is that he felt some pity and remorse for his planet.
So totally nerf Argent Defender. He's stupid.
However, if you're talking about the paladin talent Ardent Defender, it's just about right and puts paladins on a similar but not as good level of EH as a druid. The proc is reasonable and is on the same level of power as many other ohshit buttons, with the proviso that it's much better in some cases (ohai, Algalon) and not nearly as good in others.
Sorry for that. Was feeling a bit silly this morning and was annoyed at yet another stupid thread about Argent Defender, and that silly misspelling. Argent means 'silver'. Argent Crusade - Silver Crusade, kinda like that Silver Hand thing. That big burst on the tabard? It's in silver, ya know. Ardent means impassioned or hot, like...zealousness. Ya know, like what paladins are?