I use marc in silk robe since I need the MDEF in case of storm gusts or spells . Marc Wind is not used in that numbers in war.
People use either GR or MDEF armours or status armours in war. In such a situation any element will do - Fire is preferred because it can be used for busting Emps too.
Earth is effective too since only Fire reduces it by 50% - for all other elements - they are reducible by 75% by the same armour cards.