That's obvious reach in my opinion. I've fought people with extremely low ping on Manacube and they do not get hits such as those.
Just from my experience, since he jumped on the second or third hit, it usually means they have reach and know that they will get the crit to kill eveyone quicker.
People who have better ping are more likely to get the first hit but in this case the player is hitting you from 4-5 blocks on the second and third hit.
You should make a player report
here with the format provided :p
I spent time to prove he is cheating,
View attachment 7016
3 and a half blocks is where the start of the hit was as your screen rotated.
The range in minecraft is 3 blocks but you were pressing 'w' at the same time so you had momentum aswell.
Hits do not register that quick in 1.8, so if you ran at someone to hit them and they are sprinting too, the range would be about 2.6-2.8 I am assuming.
This proves that he had reach :p