Based off your lodestone I'd say you're just fine for off tanking. Garuda is more of a skill check than a gear check. If you're gear is great in your group you just kill her faster and avoid phases, but you're gear as you have it would absolutely be enough. I OT'd Garuda just fine with gear worse than yours. As for main tanking you probably have enough as well. Just avoid slipstreams and you'll be fine. Don't let everyone here convince you that you need crazy gear. Titan is the gear check. Not Garuda.