Macros for GCDs will significantly hurt your overall DPS.
Macros for oGCDs are acceptable they just limit your ability to specify which skill you want to use.

Examples:
Macro 1
/action "true thrust"
/wait 3
/action "Vorpal thrust"
VERY BAD
You are losing .5 or more seconds for every GCD aweful.

Example 2
/action "heavy thrust"
/action "internal release"
NOT GOOD
Since your heavy thrust is on a macro it wont Q up and go off instantly as your GCD refreshes and you lose a little bit of time every single GCD refresh which adds up.

Example 3
/action "internal release"
/action "blood for blood"
ACCEPTABLE
Space saver macro that works decently. Downside is you wont always wish to use BfB due to incoming mega flare or such and have much less control over which skills you use.