Originally Posted by
ItMe
So if I see the target is about to disappear (add about to die, boss about to become untargetable, w/e), and know I have 4 GCDs left, I can go 1212...[thing disappears, new target appears]...3 instead of 1231...23 and taking an extra GCD to DoT the target.
Or for War you can do the opposite and break your combo to end on 3 to refresh your buff before downtime.
It's not supah deep, it doesn't make or break your parse to any notable degree, but there are reasons to break your combo. I'm sure I could think up examples for other classes, but I don't play many at a high level lol.