What am I doing wrong with my GLA?

[Sadana]

I know those feels... I asked about this back in March. You'll find some good advice there.
http://forum.square-enix.com/ffxiv/threads/153502-GLA

I will tell you (my opinion)... you WILL have trouble holding hate against max level players as a lowbie tank (especially GLA) unless THEY watch their own aggro. I think it's a fault of the game. :/ When I tanked for friends (nearly exclusively to avoid grief), I'd sometimes remind them about the aggro thing and say I'd do my best. ^^v

to add: I open with Shield Lob (marks target 1), Flash and position mobs (might Flash twice depending), Fast Blade, Savage Blade, Flash, repeat. I will build hate on enemy 1, then smack enemy 2 with the SB part of the combo just to keep his attention as part of the rotation above. If a THM is all aoe all the time regardless or someone decides the numbers mean nothing, the mob can go chew on their face for all I care, I've done what I can (this is after many attempts to pull the mob back, of course.)