This paper reviews the state of the art in coordinated multi-robot exploration and proposes a new exploration objective based on a practical scenery, reducing the difference of waiting time among different regions of a workspace, which has not been still considered in the literature. A new global optimization strategy for coordinated multi-robot exploration based on a proper dispersion of robots in separate regions is presented. This strategy aims at achieving the lowest variance of regional waiting time and the lowest variance of regional exploration percentage. Both features reveal that the proposed strategy performs better than other state of the art approaches.