The Tigers invested £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."
Opposite number Gus Poyet admitted the sending-off had thrown his plans into turmoil, but backed his team to bounce back as they prepare for an intensely difficult trip to Manchester City on Wednesday evening.
He said: "It's difficult to analyse. Everything was set to have a great afternoon of football and after three minutes, it became really difficult.
"Playing 85 minutes with one less, it's even more difficult, so I'm not going to kill myself analysing the game because it's not worth it.
"If we can erase this and just keep believing that we were good before 3pm today and we were getting better and we were a difficult team to play against and make sure this doesn't affect anything that we were doing before."
Brown is expected to receive a two-match ban for his second red card of the season - he had a third rescinded on appeal - and will miss the trip to City and the FA Cup fifth round tie against Southampton.
Meanwhile, Poyet urged England boss Roy Hodgson, who was at the Stadium of Light, not to judge winger Adam Johnson on what he saw on Saturday after he was forced to play a different role in the wake of Brown's dismissal.
He said: "Listen, I'm sure that Roy knows enough about football to realise that he needed to play in a different position because he was needed.
"He tried his best, so maybe he will need to come back another day and see him play in a normal game."