External Storage slowing down XB1

I wouldn't take that to the bank. I just bought a Seagate 4 TB USB 3.0, in fact it's the same one Major Nelson used in one of his videos, and even tweeted out a link to it, but it will NOT work. It always comes up as a media device, you can not store games
and apps on a media device. I get no option to format it, Xbox support was no help at all on the matter, so I wish you luck.

Xbox One supports any external harddrive, be it portable or desktop as long as it is USB 3.0 .

I don't think that's a bug

One of the features of the series console is quick resume and preloading games as you download as soon as you reach 25% which requires the internal or storage cards

And downloading to external would slow down the download

You can download direct onto internal then move it externally keep in mind it's painfully slow without the compression processor at 500mbps

Sorry to hear you're experiencing this. Perhaps the issue is with storage. With 900+ DLC packages the game can take up quite a bit of room.

Perhaps try adding an external storage device if you are not currently using one. You can use a USB 3.0 device ranging in size from 256GB - 16TB in size for external storage. Hopefully, when added, you can put the game and DLC on that and no longer experience
these slow downs.

The games for 360 will slow down, as more attention is turned towards the XB1.