"When people get multi-gpu setups they already know they will going to have a hard time, no matter if it`s Nvidia or AMD."
No offense, but you are completely dismissing the currently vast gap of solid multi-gpu support between the two companies. For example, it is now almost month 5 and we still do not have a working CFX profile for Fallout 4, which is not exactly a low-selling indie release. Now, we can dump all the blame on Gameworks, but AMD did eventually get a solid CFX profile working for Witcher 3, and it didnt take 5 months. And while I dont expect to have perfect GPU scaling on day 1, Nvidia is much, much quicker at getting a solid M-GPU driver out for the latest titles.
Also, if memory serves, they (AMD) had gotten a good, solid CFX profile out for the 1.2 patch of FO4, so we cant even blame Gameworks. Since that patch, which worked for a whole 3 days before the 1.3 patch was released (or however short it was) CFX has been a hitching mess on my two 290x(s). I think it was 16.2 or 16.3.0 in which they just apparently completely disabled CFX (by default) for FO4. Not sure why they re-enabled it by default for 16.3.2, since it is still unusable for me.
BF4, was a mess all around---if you remember, it was developed as a flagship title for AMD's new Mantle API, which they couldnt get working for like 6 months after release. Not sure that's a great indication of Nvidia failing and AMD succeeding.