Though Tigers slipped a place to fifth in Betfred Super League following a 36-12 defeat two days ago, Powell felt the scoreline was harsh on his side and he believed they could have got something from the game if decisions had gone their way.
Castleford hit back immediately after Hull’s opening try, but a controversial touchdown edged the home side back in front.
There seemed to be an obstruction before Jamie Shaul touched down, but Hewer awarded the try.
Castleford were 22-6 behind early in the second half, but a touchdown by debutant Calum Turner gave them hope and he crossed the whitewash again with 17 minutes left.
That would have made it 22-16 with the conversion to come, but a touch judge indicated the winger had been in touch before getting the ball down and Hull responded with a try to make the game safe moments later.
Both decisions would almost certainly have been handed on to the video referee if the match had been televised.
Shaul’s try, in particular, angered Powell and he said: “[It is] going back to needing video referees at every game.
“It is an absolute shambles, people running outside shoulder lines and nothing getting picked up.
“I cannot believe some of the lines being run today and not picked up.
“It was a shocking performance from the guy who refereed today, in the first half, in my opinion.
“Basic things that should be picked up were not picked up.
“I thought we started the game great, our defence was pretty tough, then we lost the ascendancy from, I thought, some terrible decisions.”
Powell added: “I’d like to sit down with the referee in question and say ‘this is my opinion on what I’m seeing, what are you seeing?’
“When you’re not on Sky, it is just a shambles. I am talking about obstruction when you clearly run to the outside shoulder of a defender. I don’t know what they are doing at the minute with obstruction.
“There was one last week where Wakefield had a try disallowed for a defender on the inside of the line that’s being run getting blocked off.
“That got chalked off and I am saying that’s a try. I am saying today, their second try is not a try. Do you have blokes diving on the floor [to highlight an obstruction}? If they cannot see it, what do you do in a non-Sky game? Ridiculous.”
Of Turner’s disallowed touchdown, Powell insisted: “I have got the video up there [in the stand] so I can see it.
“I do have the replay. He should have done better, but his knee looks inside.”
Castleford were without Man of Steel Luke Gale due to a fractured kneecap suffered in the previous game against Wakefield. He joined full-back/stand-off Ben Roberts on the sidelines, along with Greg Eden, Jake Webster, Nathan Massey and James Clare. Forwards Joe Wardle and Alex Foster were in the centres and Shenton switched to the left-wing.
When Jake Trueman sustained damage to his jaw midway through the first half Shenton moved further out of position to full-back.
Castleford also lost prop Grant Millington to a head knock and were down to two available players on the bench for more than half of the game.
“I thought we were great,” said Powell of Tigers’ performance. “I thought we were outstanding in the second half.
“I am pretty proud of our effort, it was more like us. They got away from us a bit at the end, but I think that scoreline is pretty harsh on us.
“I think we’ve got a massive amount to build on there.”
McShane scored Tigers’ first-half try after Jamie Ellis’ kick was knocked back by Shenton. Ellis converted that and Turner’s score after the break, the winger pouncing following an error by Shaul from another Ellis bomb.
Sika Manu touched down either side of Shaul’s try for Hull and Bureta Faraimo also crossed before the break, Marc Sneyd – who later suffered a knee injury – kicking two goals.
Jake Connor extended Hull’s lead with a penalty and, after Turner’s try, he converted Faraimo’s second score, added another penalty and booted the extras to Josh Griffin’s late touchdown.
Meanwhile, Castleford have released winger Garry Lo at the request of his “representative” so he can focus on a “personal matter”. The Papua New Guinea international has made just one appearance for the club in their defeat at Wigan.
Hull: Shaul, Faraimo, Griffin, Tuimavave, Talanoa, Connor, Sneyd, Taylor, Houghton, Bowden, Manu, Minichiello, Handley. Subs Green, Paea, Matongo, Westerman.
Castleford Tigers: Trueman, Minikin, Foster, Wardle, Shenton, Ellis, McShane, Watts, Milner, Sene-Lefao, Holmes, McMeeken, Cook. Subs Moors, Millington, Springer, Turner.
Referee: Gareth Hewer (Whitehaven).