Originally Posted by
longtail
FA8 recharge isn't instant - the few seconds that it takes to recharge you can do another FA combo of a different rank. If you're only using one FA rank, your DPS and aggro generation will be poor. I typically rotate between FA9 and FA8, Guard and SS when available. Reckoning is typically reserved for SS (especially with multiple mobs) or FA9. Note that you can activate another combo during the finisher of whatever you're currently doing.
You should have at least two specs to switch between (can buy up to five). Since most fights involve either physical or magic damage you do not need both at once - in other words you get more out of each spec by having Iron Skin + Improved Defensive Stance against physical in one spec, and Stone Skin + IDS against magic for another spec.