Ive been trading on mercatox for almost a year,i would say that the site is legit and when it comes to kyc you dont need it to withdraw balances, maybe kyc is use only if you want to increase your withdrawal to 100 btc
Yes kyc is only used to increase your limits ( withdrew/deposit ) but kyc works different on an ico or other service . they need kyc not because of the limits but because that is their primary requirement before you can invest on them .
I used mercatox before when the time that xrb ( captcha claim ) are still popular and if im not mistaken , they dont require a kyc that time . maybe mercatox updated their rules .