The father-of-two's family are gathered at his bedside.
His sister Nayoka Toni Toleafoa-Hulton told her friends on Facebook that she was "broken" and "shattered".
"He is on life support. We are all praying for a miracle. Thank you to everyone for your love, care and support," she wrote.
"Please wake up Diego ... My heart n soul feels broken to bits.
"Love you soo much my big brother. It dosnt feel real."
It is understood Hulton had been living in Australia for about six years with his partner, son and daughter.
He grew up in Rotorua.
Hulton and the alleged attackers were reportedly at the pub watching a boxing bout between Danny Green and Anthony Mundine.
A second man was injured in the fracas, where chairs and tables were reportedly used as weapons.
Salvatore Raimondi, 32, appeared in the Northbridge Magistrate's Court on Sunday on charges of causing grievous bodily harm to Hulton.
He is also facing a second charge of assault occasioning bodily harm in relation to another victim.
Raimondi was remanded in custody until his next appearance in court on February 21.
A second man, also 32, was charged with assault occasioning bodily harm in relation to the second victim.