Though the scaling is okay at 4k. I would say it would be very, very nice to have a scaling slider/option.
That may prove difficult as I notice some things seem 'scaled up' more than others. Generally from what I've noticed it's the main HUD objects, and help/dialog text or 'pop-ups' that are small. For example the terminal, level up, quest screen, and map are all fairly dialed in for a '10 foot experience' but when it comes to the hud/help text/in-game-dialog it would be super awesome to be able to say scale that at 125%, and 150%. Also, and again just to nit pick because I'm still typing.... The hud colors are in my opinion too close to the pallets used within the world. They don't 'pop' enough for my liking, which maybe was the plan. I love the glowing green scanner text. Noms.
FYI, using 65" Sony 4K TV @ about 10 feet (or just about 3m). Windows 10, Steam, i7-6700, GTX 970. I've tried 'native' 4K and also 1080P. 4K native can be a little sluggish and it's hard to discern much when moving to 1080P. Either of which at least are a bit small for some things at my distance. I understand that this may be a design choice if this is treated as more of a traditional PC game (sitting nice and close to the monitor). Though I would like to say just how wonderful it is on the big screen, well done!