It largely depends on the encounter that you're doing and personal preference.
Astral Shift is good when you need a large damage reduction CD rarely in the encounter. Stone Bulwark is good when you need a smaller CD more often (I prefer SBT for Jin'rokh, for example, because I have it available for every Ionization whereas I'd have to cover with something else if I went Astral Shift).
And for Iron Qon, I actually prefer Nature's Guardian over the other options.
See, you mustn't take the armory at face value. People switch talents around depending on the encounter that they're at because sometimes, you might be more comfortable with a different talent or one talent that you usually take isn't as valuable.
You basically need to evaluate every encounter yourself and ask yourself what you need and what serves you best.