My MNK is only at 65 but a friend and I were talking about the Fist abilities and what-if they changed them like BRD's songs, where they completely changed their effects to all be useful most of the time and you had to rotate through them. They could also condense Riddle of Earth and Fire together, with effects that reflect their Fists.

For example: Fist of Fire could stay at a 5% increase to Damage done but it would only last for 30 seconds and when you use the Riddle ability, Riddle of Fire will grand you +10% more Damage to it (15% total).
Fist of Earth could lengthen your Greased-Lightning's effect time by like x% for 30 seconds and Riddle of Earth could just extend the time to max+x%.
Maybe Fist of Wind could deal with skill speed, attack speed, or oGCD time or something?
Then they could keep the Riddle ability at 90 seconds and make people have to decide when a good time to use it is, like if you're in a boss battle and the boss is about to become untouchable, you could pop Fist of Earth and Riddle to save your Greased-Lightning OR you could just use Tornado Kick and save Riddle for when you can damage the boss again you can pop Fist of Fire.