I’ve played a lot of WoW and more recently Destiny, and I think those are excellent examples for getting info on creating multi-user boss fights / encounters and understanding the mechanics behind them. I think anyone developing an ORPG should have some experience in an MMO to familiarize themselves with the “winning formulas” in terms of RPG design.
Additionally, Undertale is a great example of how music, sounds, and dialogue can carry a graphically and fundamentally simple game.