Willing to bet if Kench has the same build(gold) as that Naut ion that game he'd have done more damage given equal skill. I call shenanigans. Either there was a Thornmail involved. Or Shen/Kench spent half the match clumped inside his Sunfire Aura.
EDIT: LOL looked up the match. http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2142892294/210605051?tab=overview
Nautilus has Thornmail + Sunfire. You have 2 ADC champs. Ez went ahead and build Iceborn + Manamura. Shen only has Mercs for MR + Tahn has Aegis. Ahri was the only one to build any significant MR (Abysal) and did the best on your team. You didn't so much as build a Hexdrinker. 60%+ of their damage was magical. Neither you nor EZ have any form of armor Pen attacking a tank with Thornmail. How did you think that was going to go exactly?