Zenfone 2 Gaming performance

Hey guys, I bought a Zenfone 2 about a month ago. I was expecting this to be a beast especially on gaming, but for some reason, I'm experiencing bad lag on some of the games. One game where I experience it is on Eternity Warriors 4. The game runs smooth on a Note 2 and on an Xperia T2 (I think). Now I was thinking that it may be an Intel issue or something, but when I tried the same game on a Selfie (SD615), it basically had the same lag. Do you think that it's still an Intel issue, or more of an Asus firmware issue?

I love my Zenfone 2! Everything runs like a dream! Just wondering why I'm getting these lags, and why the Selfie is experiencing the same thing with a snapdragon 615.

EDIT:
Model: ZE551ML 4gb/64gb
Firmware: 2.20.40.97
Rooted: No