avast! is currently not focused in Heuristics dor Standard Shield,but in fast avast! antivirus response team to release VPS asap. There is also a very agressive generic detection method which picks even spyware and trojans so you can treat this almost as heuristic.
If the definitions part is good than you don't need heuristic module and this certanly applies to avast! (and Alwil team hehe)
But if you impliment it there wont be any damage