Tanking Gems

I've stumbled upon dodge and how it affects defense somewhere on here and was wondering if there's Agility's a better way to go with gems. Specifically talking about the 4 dodge rating+6 stamina vs 4 agility+6 stamina. Curious. that's all.
Thanks

There's a 5 dodge / 6 stam gem available from heroic SL as well.
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