Right now you pretty much put up fire and forget about them. It is rare that earth will save you from something that wont kill most of the other dps/heals anyway and wind doesn't make you run fast enough to make a difference in boss fights since the areas we fight in are small... also shoulder tackle.
I have seen a few suggestions I like and have some of my own...
Option 1: Our main AoE attack is earth and arm of the destroyer looks like it could be earth related. I think going with that theme it would make sense to give Fists of earth a damage bonus to our AoE, a TP reduction on our AoE or some combination of the two.
Then add a skill speed bonus to Wind. To balance this with Fire we would probably need some of our overall damage pulled back out of GL and put into Fire.
The idea here being Wind for getting GL up and Fire when you can keep it up. Then Earth for when you need aoe damage.
Option 2: Remove fire and add that damage back into GL or wherever is needed to keep our damage at the same place it is currently. This would leave us with being able to choose between Wind and Earth which is far better than our current options because the current option isn't really an option. Fire is best almost always.
Option 3: Remove fire and add that damage back like Option 2. Add "Fists of Water" with the effect of a small % snare and threat reduction.
Option 4: I saw someone else suggest this and it sounds great however for it to be balanced we would have to have some of our own damage nerfed and I don't like that but.. Change our Fists into group buffs related to what they do for us. Short duration buffs with a cooldown or permanent buffs. Pretty sure this would make monk required for raids and that isn't what should happen.
Option 5: Remove them all. I like the animations and the abilities sound cool but the majority of their use is when I am bored waiting on people to finish their cutscenes.
The Fists are not in any way game breaking but they are something that should be looked at. I am sure lots of people have lots of ideas on how to make these better... pretty much anything except fire all the time would be better imo.