I use macros for a lot of UI elements (such as hiding hotbars etc)..
In addition to this they are very useful for the random Off-GCD skills such as Cover, Goad, Shadewalker, Smokescreen, Warden's Paean etc - so you can use the "Mouse over" targeting system rather than having to physically switch targets..
Another use for them are for jobs like WAR where Defiance and Deliverance alters the skills you have access to. My stances are macro'd to switch Fell Cleave with IB, Decimate with Steel Cyclone and vice verser - so I do not have to find 2 additional keybinds just because I am in a different stance..
There are absolutely good uses for macros on battle classes, beyond crafting and UI, just have to be smart about them and not chew up that precious GCD delay with macroing GCD based skills.
With as many jobs in the game as we have, plus crafting macros, UI macros etc - I can totally see how you can fill all of those slots up.
(I was getting close before I had to format my computer and didn't back it all up).
Though you absolutely shouldn't be using them for GCD based skills.
Not true.
This only applies to GCD based skills. Hitting a macro between GCDs does not affect the queue system (which is where the problem lies). The issue is that macros cannot be queued.
For example..
If you have a macro that uses a GCD skill, the skill will activate before the GCD completes - rendering the macro a failure and the skill doesn't activate. Hence the need to "spam" a GCD based macro in order for it to activate. Since this is the case, server latency takes into effect and your action will be delayed 300-500ms after the GCD completred.
Off GCD skills however do not have this rule, as the off-GCD based skill CAN be activated while you have an active GCD (provided your character is not slightly animation locked by the previous skill). Therefore you can hit a macro and the off-GCD skill will activate during the GCD. You can then queue a non-macro GCD based skill afterwards without any detrimental effects with server latency.