I only use GLA as a DD now. While some people think missing out on Spirit's Within would be damage crippling, that's not so.

When you have Blindside, Invigorate, Blood for Blood, Hawk's Eye and Keen Flurry, you can do some pretty amazing damage.

Use Keen Flurry and Riot Blade from behind, lower the enemies defense, then use Riot Blade again with Blindside and Blood for Blood for some very high critical damage. Flame Sergeant's gear can enhance this tactic. Use Bloodbath in conjunction with this for a very nice, MP free self heal.