Hi. Since my post about maximizing dps I have learned a few things about stacking for tanks I'd like to share.
This will not be as extensive due to some time constraints at the moment.
I had an opportunity to off-tank ICC a few weeks ago and learned some great techniques. Though what I'm going to share is primarily for prot warriors I'm sure there are many that can be utilized for other classes.
Glyph - specific to prot warrior is Glyph of Blocking. Increasing the block and duration of your shield slam.
Next is to either use Greater Rune of Warding or even Lesser Rune of Warding. Either will give you a small amount of damage absorption. And remember, anything is better than nothing, no matter how small.
Third is potion stacking. The potion most useful seems to be indestructible potion.
Use Shield Slam whenever it becomes available, or right before you taunt when you're swapping tanks.
Follow this with the potion during critical times in a fight can make the difference between a wipe and a successful boss kill. Such as during the 3rd inhale in the Rotface encounter. I learned the hard way on this one.
I'm sure there are other tips and tricks that can be applied but so far these are the crucial new ones to me I wanted to pass along.