The only time I have threat issues is when I am tanking with an Ifrit weapon and the DPS are equipped with +1. There is a very low error margin, one mistake on your rotation or blowing a CD at the wrong time and I lose the mob's focus.

I also find that when tanking on a warrior it is more difficult to establish a threat buffer since warriors have a longer rotation (assuming you butcher block combo then storm's eye combo then butcher's again) and storm's eye doesn't produce extra enmity. Meanwhile PLD is simple 1-2-3 and Flash spam that doesn't break combo without needing to worry about maim and the slashing debuff. If storm's eye gave extra threat bonus with combo it would be much better.