for no-expense-spared balls-to-the-wall tanking i went
elixir of major agility for the battle and
elixir of major defense for the guardian.
it's also a good idea to pop
ironshield pots every cooldown for bosses with lots of physical damage (hkm, gruul, prince.)
those three combined will give you roughly 1% dodge, 2% crit, and 3120 armor. not too shabby.
if your mitigation stats aren't that important, and the encounter is more based upon everybody doing everything right at the right time (like moroes or mag) then it's much more economical to just flask for the night.
Edited, Jan 2nd 2008 3:49pm by axhed