balancing agility/dodge vs stamina while levellingFollow

I'm still in the process of levelling my way through Northrend (and loving every minute of it).

Although I'm questing in kitty form and gearing for that, I'm also keeping an eye out for suitable feral tanking gear for instances, and I'm a little confused as to how much importance I should put on agility when compared to stamina, especially as a better upgrade is always just around the corner..

A good example of what I mean is comparing:
Canyon Runner"s Vest
vs
Skarvald's Dragonskin Habergeon

The first item has way more stamina, however the second has better agility (for crit, AP, dodge and armour and also more attack power, but around 600 less HP.

I'm not really after advice as to which armour is better, but these two pieces illustrate my question... how much stamina can I afford to lose from tanking gear in favour of other tank-worthy stats, before I start to compromise my ability to soak damage?

Thanks again, Horsemouth for some great advice.

Looks like I was approaching things the wrong way.