I would have to say the pacers and if the nets play well together they have a shot as well. The thing I like about both these teams is they wont get out and run with the heat and that is how you beat them. OKC tried to run with them and got slaughtered. The Mavs didnt go out and run and they beat them. The spurs didnt go out and run and took it to 7 and shoulda won the series.
Both the pacers and nets wont run with the heat because that plays to their greatest strength and that is the last thing you want to do. Slow the game down with your bigs and have efficient guard play is how to beat the heat. The pacers did great with slowing the game down and feeding their bigs. However, their downfall was lack of efficient guard play. Same goes with the spurs when they fed Timmy and Parker and green or even ginobili came to play from the guard position they had the upper hand.
In the west Im not sure who could really beat the heat. Last year I really felt the Spurs had a chance and they did, but just fell short. This year they are another year older and that is never good. OKC just doesnt match up well against MIA . They would need ibaka to show up and play really well, and then have Westbrook and Durant avg a combined 65 points a game to even have a shot. Memphis is intriguing because they have bigs and MIA made Roy Hibbert look like Hakeem down low, so Marc and Z-bo could have a field day, problem is outside of that they dont have much of an offense to count on.
Really have to see how the heat play this year though tbh. I truly feel that they wont be as dominate this year with wade getting older and bosh drifting further and further into the abyss. Lebron is gonna have more and more pressure on him and that is fine he can handle the load, but only to a certain degree. If by the time playoffs role around and the heat play as iffy as they did in the eastern playoffs last year, I think the nets and pacers can both give them a run for their money. If rose is healthy maybe the bulls I just think rose with Bron on him is a really big task for rose to deal with.