Huddersfield were well worth their lead fashioned from a fine sweeping move down the left which finally saw on-loan Middlesbrough defender James Husband square for Paterson to find the bottom corner for 12 yards to mark his 200th career appearance.
After visiting manager’s son Alex Bruce fired over from six yards on the stroke of half time, it looked as if the Tigers’ poor run of results was set to continue.
It took some fine saves from Allan McGregor to keep the score level before Hernandez equalised.
It looked as if Huddersfield had then won it when Harry Bunn’s left-wing cross was turned into his own goal by Maguire, but substitute Diomande headed home a deflected header at the far post to secure a draw.
Hull remain fourth, nine points behind second-placed Middlesbrough while Huddersfield, who came into the game on the back of successive defeats by Middlesbrough and Sheffield Wednesday, are now nine points clear of trouble.
Huddersfield boss David Wagner told BBC Radio Leeds:
“I am long enough in this business to know it is only over when the final whistle comes, but this is a very strong side.
“We were a little bit unlucky that there was a touch and we were not unable to avoid the header, but mistakes happen. It is part of the game.