"We're pretty good when we're healthy but we're not where we need to be," Dallas coach Avery Johnson said. "We aren't anywhere close where I need them to be. If we had to start the playoffs tomorrow, I would really be concerned, but again, we've got some time."
Now in his third season with the Mavericks after playing his first five with Atlanta, Terry hit two 3s, a 12-footer and a pair of free throws in the final 3:54.
Dallas' biggest lead came at the 5:16 mark of the second quarter, when Howard's turnaround jumper made it 51-28.
After Terry's 14-footer gave Dallas a 73-63 lead with 2:52 left in the third, the Mavericks scored just one field goal over their next 12 possessions, a stretch that included five turnovers.
"We had some sloppy issues there, and they dominated us at the free-throw line," said Johnson, whose team improved to 33-3 when scoring at least 100 points. "They shot 49 free throws, and guess what? They deserved every one of them. We were out of position. I actually told the refs twice, 'Good call,' because it's stuff that we've been teaching."
Josh Childress' dunk gave Atlanta its only lead at 79-77, but Terry, drafted 10th overall by the Hawks in 1999, answered 22 seconds later with a straightaway jumper.
Following a pair of free throws by Howard with 7:44 remaining, Dallas never trailed again. Terry was still mad at himself for trying to force the pass to Nowitzki that Josh Smith stole and passed up the court for Childress' dunk.
"I was trying to force the ball where there wasn't an opening," Terry said. "So I took it upon myself to be more aggressive, look for my shot.
Atlanta has lost three straight, five of six and 13 of its last 19 games.
Childress and Josh Smith each scored 21 for the Hawks. Marvin Williams cut the lead to 86-84 with 5:26 remaining before Nowitzki answered with a straightaway 3-pointer.
"They beat you in so many different ways," Childress said. "I think their pace offensively makes them very hard to guard. They're moving around and when you get to rotating, a guy hits a wide-open 3 or a guy is slipping to the bucket. Their offense is kind of centered around the elbows. It's hard to guard the elbow."
Dallas' 39-point first quarter was the most prolific opening period this season for an Atlanta opponent.
"We didn't give up," Smith said. "We played well for three quarters. The first quarter kind of hurt us. We put ourselves in position to win the game, and when we messed up on a couple of switches at the end, it kind of cost us the game."
Johnson, who celebrated his 42nd birthday, improved his regular-season career record to 134-35. ... Hawks coach Mike Woodson dropped to 66-169. ... Mavericks G Devean George, who missed the last six games with a sore right knee, finished with one rebound and three fouls in eight minutes. ... The Mavericks are now 46-0 when having a better field-goal percentage than the opponent and 37-3 when having 20 or more assists. ... Dallas has won four straight in the series and 14 of the 17 against Atlanta. ... The Hawks fell to 6-10 this season without G Joe Johnson, their leading scorer.