Console Local Coop

It would be great to play with my brother on the same PS4, like a split screen or another way.

D3 has Local Co-op, and it's pretty awesome.

It would be nice to have in PoE, but don't hold your breath. They hardly ever work on issues related to party play even on PC, let alone on Console, and this would be Console specific.

If you've got the money, and really want to play together, get a 2nd console and a 2nd TV.

At least PoE is 100% server-side, so you can log in from any console and all your progress is there.