Yep, unfortunately Total Mayhem is a bit… “controversal” with both the community and the development team. See Game Director’s Jeff Kaplan’s comments about the mode here:
Hi there! I think it’s awesome that you enjoy Total Mayhem so much. I am extra critical of it because I literally implemented that mode (I don’t get to do a lot of implementation on the game anymore… and I miss it!). I made the mode very early on, when our technology was nascent. We didn’t have a lot to work with and it was a very simple thing to put together. All in all, I don’t think it plays well and has a host of problems. I feel like it’s the type of mode that belongs more in Custom Game. I get that people enjoy it – and that makes me happy… but if it weren’t for it’s legacy, I would simply retire it permanently to a Custom Game mode.
Lots of people like a lot of different modes and we try to make space for as many of them as we reasonably can. Hopefully more people will go to Custom Game for these type of modes.