Are you having a little trouble with the maths there?
You're saying that overclock puts the 970 at 10-15% faster than a stock 980, and you're saying a 980ti is about 25% faster than a 980, which means that 970 is only 10% or so slower than a 980ti at stock.
Now the RX480 is 30% faster than the overclocked 970........ that would put it way beyond the 980ti by your numbers, which I have no idea if they are correct.
Though again it's worth noting that the RX480 is probably limited in max frame rate as it never exceeds 62fps that I noticed and never went below 58fps.
Also the 970 rarely hit 50fps, was at 44-50fps when essentially no action was happening but spent almost the entire time during action at 39-41fps while the RX480 didn't dip under action. So during action when performance both matters more and is more noticeable, the RX480 was a full 50% faster consistently.
Probably also worth noting that in such a scenario the RX480 performance/watt is drastically improved.
http://www.tweaktown.com/guides/7655/quantum-break-pc-performance-analysis/index2.html
Broadly speaking comparing to those numbers a 970 SC gives about the numbers indicated 37fps low 42 fps average as the 970 in the video achieves. The 56mins the Titan X achieves would suggest the RX480 has slightly higher minimums and slightly lower average, if the minimum in the vid was 58fps, either way the cards would be pretty close.
We already sussed this soon after the post. At 1080p the 480 would surpass even the TI in this game with those clocks. (stock TI).