All three made their first starts of the season, with fly-half Humphreys - in his first league start on home soil - collecting the man-of-the-match award after contributing 16 points with a perfect record from six kicks at goal. Scrum-half Murphy and hooker Hickie were also part of a solid team performance.
"I thought all three took a massive step up in their development," said Howard after watching his side move into fourth place in the table. "Those guys came to the club as number threes and have shown a fair amount of character to step up and show there is no massive gap between number one and number three in some positions.
"They have had the right attitude and I have been impressed with them from when I first got to know them.
"As a team, we were good in parts and we played with some ambition, particularly in the first half though it was quite tough into the wind. We were not as clinical as we would have liked and turnovers in the first half cost us but, considering how many players are away, I was quite happy with the performance and happy for the guys who stepped up."
Winger Tom Varndell scored both Tigers tries as the team secured their fifth Guinness Premiership victory of the season.
"I am very pleased for him," said Howard. "Tom has come back into the team as a better footballer. We know he can finish and we want to see more of that, but his footballing skills are improving. At 21, he is becoming a better player, but he is also humble enough to know he can improve again."
Varndell's opening try came as a result of a lengthy break by Dan Hipkiss, while the second came out of the blue as he chased a Humphreys kick which threatened to go dead before the England wing stunned the Irish defence by diving on the ball.
"The second try was a great tribute to Tom's enthusiasm in chasing the kick," added Howard.