This Supposed To Happen?

[Inferno]

Every now and then i like to play solo just for a laugh owning them on beginner and some times i use mutators.Clot-Buster i think its called only spawns clots but on the 4th wave its all clots till then then it changes and there will be clots and fleshpounds sometimes more then it goes back to normal till about wave 7 then its everything again is this a bug or is it supposed to happen so its not to easy.
Thanks
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Inferno