Excimer laser homogenizers based on microlens arrays (MLAs) are significantly influenced by the spatial coherence of the source, which can induce interference fringes and increase the non-uniformity of the output beam. To address this issue, a theoretical framework was developed to model excimer laser propagation in the homogenizer with random phase plate (RPP) modulation and to establish a Latin hypercube sampling (LHS)-based optical tolerance evaluation scheme. Furthermore, a RPP design based on the hybrid particle swarm and grey wolf optimization (HPSO-GWO) was proposed, achieving a homogenizer output beam non-uniformity of 1.82%. Finally, the effects of RPP assembly tilt, decenter, and manufacturing tolerances on homogenizer performance were individually assessed, followed by a variance-based global sensitivity analysis to quantify the contributions of each factor and their interactions.