I wouldn't say that a reduction in health wouldn't be a bad thing. But another thing that could be done. Is that once the wisp phase is complete. The crystals should be destroyed instead of waiting for the timer to end. Now I could be missing that people are not back, and some are having trouble with it. But once it is complete, we shouldn't have a time eating phase of waiting on the crystals.
But I get that is is a long Meta, and we are not unfamiliar with this. Example being Dragon Stand. That Meta takes on average from my experience, about 35 to 50 mins. But that is because it has been out for a while, and we have mounts to help it along. But when it first came out, it would take close to the full 2 hours of time given, especially when people were figuring it out. But I'm say that the fight needs a little more time, not the whole meta.