Hosts Villa took the lead inside the first minute through Ashley Westwood, but Hull hit back when Jordan Bowery deflected Liam Rosenior's cross into his own net shortly before the half-hour mark.
It looked as though the sides would go into the interval locked at 1-1, but two Andreas Weimann headers late in the first half put Villa in control.
The defeat means that Hull are yet to be assured of their top-flight status next season, although they will be secure if Norwich City fail to win at Chelsea on Sunday.
Bruce, however, was less than impressed with his side's defending.
"The way we started the game was the way we finished the first half, so sloppy and awful in our defending," he told reporters.
"The reason we've got to where we've got to is the ability to be resilient and defend right and we were awful in that department.
"That's not just the back three or four, it's the whole team, we didn't get started.
"It would have been interesting to go in at 1-1, but we have to be honest and say after the way we've played today we didn't deserve anything more than we got."
Bruce felt there was a foul on Curtis Davies in the build-up to the opening goal, but the Hull manager refused to use that as an excuse.
"I don't think that makes a difference, we've made mistakes after that," he added.
"We haven't done enough to win the game. We haven't defended well enough and we've gifted them two goals.
"All in all we have to hold our hands up and say defensively today we were nowhere near where we've been for the season."