Robots and robotic systems have become an inevitable part of modern industrial settings. Robotics systems are being introduced for various household services as well. As the interactions between the workspace of robots and humans increases, there is an increased likelihood of unintended harm being caused by the robots to humans due to collisions or abrupt contact. To mitigate this, active and passive compliant mechanisms must be introduced in these systems. In this study, a design optimization case study is carried out for the optimization of a passive compliance mechanism achieved with variable stiffness joints realized by the use of permanent magnets. Three design parameters of the systems, namely, inner stator width, outer stator width, and magnet height, are considered. The objective is to minimize the weight and maximize the maximum torque. A nature-inspired metaheuristic hybridized with a multi-criteria decision-making method is introduced to achieve this. The Non-dominated Sorting Whale Optimization Algorithm (NSWOA) is used for Pareto optimal front generation and MARCOS (Measurement of Alternatives and Ranking according to COmpromise Solution) is applied to extract the best feasible solution from the Pareto front. We observed 1.8% and 41% improvements as compared to the previous known best design and original design, respectively.