It takes approximately six hours to get from Level 75 to 95 using this method.
Skip the cutscenes after the boss, save game, and reload from main menu. You can also do other things while doing this, such as watch TV. During the boss fight, skip through all cutscenes, lock on to the boss (R3), and hit him with fast attacks (press Square). Finally, assign six people to the Sage's Salon. Also, research everything at the Basic Training Ground and Officer's Training Ground. To maximize the XP earned, set the Tactics Tweaker to favor XP, craft 3x 'Necklace Of Enlightenment' at the Evermore Outfitter, and equip it to your active characters. He can be replayed an unlimited number of times and gives half a level-up each try (takes approximately five minutes). The quickest leveling method is to repeat the final story boss. That is still a long way from standing a chance against the toughest monsters. After getting a 99% game completion (all tainted monsters, side quests, and story chapters), you will just be around Level 75. While you can complete the story at Level 55, there is still a lot of endgame content that goes well above Level 90, such as the Tainted Monsters #51-60 and 10th Dreamer's Door Maze (which has a Level 95 boss).
