There are many, many, many reasons why macroing any GCD skill is bad, not to mention an entire rotation. As others have said, you can only have a delay of whole seconds in a macro. Your GCD will not be exactly whole seconds no matter what you think. On top of that, your lag to the server will artificially increase your GCD.
Macros cannot know your GCD. They cannot know your skill cooldowns. The macro will literally wait the time specified, and then try to execute the action. If the action is off cooldown, nothing will happen, but after the next delay specified, the next command will be attempted. In other words, macros do not "queue" moves.
If you are using skills manually and you hit a skill that has 0.5 seconds or less remaining on the cooldown, the skill will flash and then the second it finishes cooling down, it goes off. This is called "queuing" a move, and it not only eliminates any delay due to user input, it also eliminates any delay due to latency because the queuing happens on the server. If you use a macro, it can't queue because the game has no idea what skills are being used in the macro since you can have several or none. So, even if you have a single skill macroed (something like /ac "Spinning Edge" <t>, /p "Ha! Take that, evildoer!"), if you hit that macro when a skill is 0.1 seconds from cooling down, it won't do anything. Because of this, macroing GCD skills at all is a major DPS loss.
The upshot of all this is that if you use macros like this, you might as well remove all skillspeed from your gear and stop using Huton because you are completely eliminating any benefits from those to your DPS. This macro will significantly lower your DPS in all content, especially late game content, making you a liability to your group in any DPS check scenario. In any situation where you have to move as part of dealing with mechanics, it'll be even worse as you miss parts of your combos due to positioning.
In short, don't do it. Don't use macros for rotations. Don't use macros for any GCD skill at all.
Only macro really important skill uses that your party needs to know about, like Hallowed Ground (PLD), Berserk (WAR), Raise/Resurrection (WHM/SCH/SMN), Cometeor (BLM/SMN in PvP), and so on. NIN has only two skills that fit this criteria that might be useful to announce via a macro when you use them: Goad and Trick Attack.
Macros are also good for skills you want to use on a mouse-over target, like Aetherial Manipulation (BLM) or Cover (PLD) - you can set it so hitting your middle mouse button while hovering over a person (or their name in your party list) will cast the skill on them. I don't think NIN has any for this since their movement skill is a ground target. Maybe Goad, so you don't have to deselect your current target?
So, a good NIN macro could be:
/micon "Goad"
/ac "Goad" <mo>
/wait 1
/p Goad used on <mo>
(the wait is there so if you spam the button, you don't spam your party)