Troy Deeney scored twice while Mark Yeates and Matej Vydra were also on target, leaving Marcus Tudgay's stoppage-time goal as a mere consolation.
"There was nothing even about it. We rode our luck with respect to the first half," said Hill.
"We made some horrendous decisions in and out of possession. The best team won and I've got to congratulate Gianfranco (Zola) because I think he's got an excellent side.
"We were very susceptible. We looked weak against the opposition so I don't think we were ever in the game.
"Individually and collectively, we weren't cohesive today, with and without the ball."
When asked if Watford are good enough to secure promotion this season, Hill added: "There's a possibility.
"That's the best performance I've seen from an opposition team. I thought they were excellent in every department."