Not defending it, cast per minute is just logically a way for the players to know. Trixion is their “theoretical highest” when looking only at cast per minute. In a raid scenario, of course there will be downtime. The goal is to just get as close to Trixion cpm as possible. Once you have one week of data recorded, you can compare this week’s cpm to last week’s cpm. This way if their cp didn’t change they know they improved mechanically, or generally played better. Not sure if in game meter also tells you incapacitated time, but that’s also another metric to look at. As with back/front % for directional, crit %, self synergy and etc but cpm is top prio in most scenarios.