Hi there. I've been playing a Shadow ever since.. but I am still clueless about some things and I need your opinion on this one.
If you are in tank spec and tank gear, is it better to have endurance augments or go with the Defense rating augments?
Endurance is among a tank's primary stat so fortitude 22 augments are the way to go. The other stats are obtained via mods and enhancements. My two cents, people may disagree and there is no one way of doing your toon. There are many ways of making a tank and being successful. I do not agree with kitru that you need 60 absorb. 50-55 is enough as long as you got 30% defence and hit high on the HP pool.
There are attacks that are not mittigated at all so a 26k tank vs a 31k tank will behave differently. While the healers are happy with the former, takes shorter to top up, the raid will benefit more from the latter as it will have more flexibility in these cases.
There are some BEST IN SLOT mods and enhancements. The first one that comes to mind is the 27B which is a must for a shadow tank.