MCT is a widely used heuristic for scheduling tasks onto grid platforms. However, when dealing with many tasks, MCT tends to dramatically delay already mapped task completion time, while scheduling a new task. In this paper we propose heuristics based on two features: the historical trace manager that simulates the environment and the perturbation that defines the impact a new allocated task has on already mapped tasks. Our simulations and experiments on a real environment show that the proposed heuristics outperform MCT.