Depends on what content you're in and how quick/comfortable you are with your control scheme and tracking your cooldowns and such.

I would never suggest macros for your rotation combos. Like Remn said, macros can't fit the GCD that closely. They also tend to bug out if you spam them (you can have a three-line macro, and have the 1st line miss and the 2nd line fire if the timing on the GCD splits just right). And it leaves you unable to adapt if you need to delay one move or another for some reason.

Macros for communication are a good idea, but they're really not necessary until you're doing raids or primals. They can be nice for dungeons, but the difference it would make there is pretty minimal, IMO.

Macros for stacking cooldowns or throwing cooldowns in with rotations, or for making targeting easier, it depends on your class and how much space you've got on your bars, how fast you can hit them, how well you can track them otherwise, etc. I used to use a few cooldown combination macros on my Warrior, but I don't anymore. I just don't have trouble tracking my CDs and keeping them on separate buttons. On my White Mage, I use target-of-target macros for my damage spells, because I just hate the process of switching from targets to heal to targets to harm and back.