Personally to me happy hour should just boost the rates of drops in older maps for a while to make them an alternative to farming from the usual maps, such as increasing their drops rates or adding generic drops to the global drop table for a while. When popular, current maps are on happy hour, the maps are just even more desirable and the intensity of people farming there increases a lot - there's always people doing illusion dungeons and biosphere and when those are on the happy hour map pool. They become flooded and awful to play in as everyone is dropping big AoEs that clear the enemies out instantly. If you're not very well geared or not a big AoE class, you're basically locked out of participating at times.
This might change if there are multiple good options during happy hour, but usually what happens is the map pool is full of dead fields that no one would ever go to and then one high density map or current level map and the entire server who are currently active flock to it. Or there's nothing worth visiting so it's ignored besides from people gambling on getting a random cash shop item even if it's not efficient to do so. It's not very interesting.
