The Prism is not a "best" class. It is a modular engine. Master the Fusion timing, and you will out-damage the Blinkblade. Mis-time it, and you will exhaust by room two.
If you enjoy having a solution for every problem, a build for every scenario, and the ability to single-handedly control the ebb and flow of a battle, the Prism is the class for you. Embrace the complexity, and you will become a legend of Frosthaven. Now go out there and show them what the H.I.V.E. can do. frosthaven prism guide
If you want to dive deeper into the world of Frosthaven and optimize your campaign, there are several great community resources you can use to check monster AI or scenario maps: The Prism is not a "best" class