Thank you very much! I thought [nochanneling] only worked with actually channeling spells like mind flay, drain life etc. Didn't know it worked for hard casting! I will test it when I get home!
/cast [mod:shift] !Fire and Brimstone
/cancelaura [nomod] Fire and Brimstone
After some additional testing I think you are right in saying that [nochanneling] only affects channeled spells.
After 5.3 hit I just played around with F&B macros and sometimes I interrupted my own casts using the above macro.
Then I just tried to modify my macro and added the [nochanneling] whereupon it seemed to be working without interrupts.
But now I know it better:
The macro allows spamming as long as you use it for aoe purposes, because of the "!" in front of the F&B, which prevents using F&B again, when it's already up.
The macro interrupts your spellcasts when you want to switch to single target and F&B is still up. This is, because F&B needs to be up until the cast modified by it is finished (The new F&B costs no embers, but the casts modified by it). So when you spam the single target version of the macro with "/cancelaura F&B" it will just do that and you can't finish the F&B cast, because F&B is not up anymore. I wish it would be possible to convert an F&B Incinerate into a normal Incinerate when cancelling the F&B buff^^
1: Spam the macro while aoe-ing
2: When you want to switch back from aoe to single target and you are still casting an F&B Incinerate, wait until the cast is finished and then spam the macro for single target again.