The Tigers invested B£13.5million in the two strikers last month and have reaped an early dividend with both scoring in a 2-0 win at the Stadium of Light.
Bruce said: "All credit to the people who employ me to have the vision to go and do it.
"It's paid its reward today. Longy has got two in two and it's the way they play and the way they are as a pair.
"They work hard for the cause and they are a good pair of strikers. I wouldn't want to play against them because they caused all sorts of problems today.
"If you look at all the bottom half of the division, we all can't afford a (Sergio) Aguero or an (Alvaro) Negredo or a (Luis) Suarez, and that's the hardest part.
"I have always said, even in my Sunderland days here, you are only as good as your strikers, and I have still got that belief now.
"For all the wonderful possession we had, we still needed to stick the ball in the back of the net and they have done it today."
Sunderland's hopes were dealt what proved to be a fatal blow with just four minutes gone when central defender Wes Brown was sent off after felling Long after he had intercepted Phil Bardsley's ill-advised back-pass.
It took Hull until the 16th-minute to make their numerical advantage tell when Long flicked Jake Livermore's scuffed shot into the roof of the net.
The game was over as a contest when Jelavic headed past keeper Vito Mannone after Maynor Figueroa's 62nd-minute shot had looped up invitingly off substitute Santiago Vergini.
Asked if the win was all the sweeter because of the nature of his exit from Sunderland in November 2011, Bruce said:
"A lot has been said. I have just said walking up the stairs, the last time I came here, I needed to have a police escort to get home.
"That was two years ago. A lot of water has gone under the bridge since then. I'm not going to be the last or first Sunderland manager sacked.
"It's no sweeter than winning anywhere, believe me. But it was the manner of it which pleased me today."