Humphreys meanwhile replaces Nigel Davies in the West Country after the former Wales centre paid for Gloucester's poor season with his job.
And Hook, who has won 76 caps for Wales, is confident that Humphreys is the man to turn their fortunes around ahead of the new campaign.
"As a player his record spoke for itself and then you see what a fantastic job he did at Ulster. The work he put in there was incredible, it's an exciting appointment," he told the Gloucester Citizen.
"I haven't met him, but from everything I have heard from other people, he has been outstanding and it can
only be good for the club.
"He had Ulster going stride for stride with Leinster and Munster. You only have to look at them in the Heineken Cup to see how good he is because a lot of that is down to David.
"There's no reason he can't bring that sort of success to Gloucester. He's ambitious, he wanted to move to the Premiership and I'm sure everyone at Gloucester is looking forward to working with him."