The rule of thumb is that if you can do something with an in-game macro or add-on, it's okay; if you can't, it's not. If you follow that rule, and err on the side of caution if there's ever any doubt, you should be fine.
In other words: yes, this will indeed get you banned if you're caught, because you're relying on casting multiple spells with a single keypress, which cannot be done using the in-game macro system.
Of course, even if this sort of stuff was allowed, or you (one way or another) manage to never get caught, it's generally not going to be possible to make such a macro anyway. Your latency is never constant, and any deviation in lag changes the time you have to wait before casting the next spell; cast too early, and the previous spell is still in effect; cast too late, and you're potentially wasting time.