/castsequence & /cast, weird behaviour

[Fomeny]

Good day,

since I'm a lazy player I recently tried to set up a one-button-dps-macro on my Warlock. Actually it works somewhat, but there is some odd behaviour I don't understand. I made the following macro
(note: Translated into english, so if the name of spells doesn't exactly match, this wasn't the problem,
note2: I made this one out of my head, so it may not be 100% accurate, I'll double check when I get home)

-------------------------
/castsequence immolate,chaos bolt,,incinerate,incinerate,incinerate,incinerate, incinerate,incinerate
/cast conflagrate
-------------------------

Explanation: I expected the macro usually to stop in the "castsequence"-line as long as it has something to cast. Further I expected the conflagrate to hit 'between' the double-semmicolon (,,). This wasn't the case. Pushing the button consistently resulted in this:

Immolate --> Chaos Bolt --> Incinerate --> Conflagrate --> Incinerate

I simply can't understand, why one incinerate hits before the conflag... This simply doesn't make any sense to me. The original idea for this setup was the following: Conflag should be casted whenever it's up and available (meaning: Immolate active).

Since you can't use:
-------------------------
/cast Chaos Bolt
/cast Incinerate
-------------------------
anymore, as it stops on the first line, I tried to make a workaround, that simply uses Chaos Bolt when it's up. Actually I succeeded with the following macro:
-------------------------
/castsequence Incinerate,
/cast Chaos Bolt
-------------------------
So I thought, the one-button-dps-macro might be similarly achievable...