as you mentioned "as long as you wait for GCD to finish"
would it perhaps work to add some extra comma's, to prevent an extra keypress from making it to the end of the list.

ie.
Quote Originally Posted by 'Ghallo',index.php?page=Thread&postID=160060#post1 60060
Code:
/castsequence [target=player] reset=15 Renew,,,,,,, 
/castsequence [target=party1] reset=15 Renew,,,,,, 
/castsequence [target=party2] reset=15 Renew,,,,, 
/castsequence [target=party3] reset=15 Renew,,,, 
/castsequence [target=party4] reset=15 Renew,,,
just brainstorming with you at 2am drunk and tired.