Ayoze Perez's strike on the stroke of half-time gave Newcastle the advantage at The Hawthorns, with captain Fabricio Coloccini making sure of the points for the visitors with a second-half header.
The result made it five wins in a row for Newcastle, but Irvine's men have now claimed victory in just one of their last six games.
West Brom striker Saido Berahino went into the game having scored five goals in his previous five Premier League games, but was kept at bay by a stubborn Newcastle defence.
Irvine rejected the suggestion that Berahino's call-up to England squad was the reason for his quiet showing and is keen for his side not to become overly reliant on the 21-year-old.
"He probably had his poorest game, but people have poor games," Irvine said. "People will ask the question 'is it as a result of what's just happened to him during the week?' but you can have a poor game at any time.
"I'd like to think that what happened during the week has given him a massive boost.
"We need goals from all over the team. The only pressure that should be on Saido should be to perform at his highest levels as often as he possibly can and from the start of the season he's done that on a consistently high basis.
"It's vitally important that goals come from throughout your team.
"We've got players that can score goals, in midfield and so on, there shouldn't be a complete dependency on Saido scoring the goals."
The Scot blamed the defeat on a lack of intensity from his players and labelled Perez's strike as the key moment in the contest.
"We didn't play well enough," he added. "We didn't play with the right tempo or intensity for long periods of the game and in the periods where we were playing with that we lost momentum by giving away a few fouls in quick succession.
"I thought it was going to peter out and be 0-0 at half-time and of course the goal right on half-time was a big boost for them and made life more difficult for us."
