Low level tanks (pre-tank stance) have a very hard time holding threat after the nerf

[Rongway]

Low level PLDs do have legitimate difficulty pre-tank stance. At 15 running Sastasha on my PLD I could barely keep up with the healer and dps using my enmity combo (pre-RoH).

Fast Blade > Riot Blade does more damage than Fast Blade > Savage Blade. Before Rage of Halone, and even for a while after, you should be Flashing away between 50% and 66% of your MP and then recovering it with Riot Blade.

"Sure if you want things to die super slow" is the reply I usually get to that, but the tank's job isn't to kill the things; it's to make sure the things don't kill everyone else, and the 175 potency per GCD a GLA can do with Fast Blade > Savage Blade is nothing compared to the potency per GCD lost by healers and DDs when the tank isn't doing his job.