First, let me say that I love the event. It was a great idea and I'm having fun with it! It has really encouraged people to visit dolmens and dungeons that otherwise remained barren.
But, I have a suggestion. While the polymorph has nice - for the first 30 minutes - it's gotten old now. Having NOTHING but skellies in the same robes at every dungeon, dolmen, town and world boss has gotten REALLY old, REALLY quickly.
For the next go around, might I suggest making a random polymorph into a holiday event related creature. For instance, instead of every time polymorphing into a skellie, there are so many other options for a Halloween (Witches) event. Hags, zombies, ghosts, werewolves, etc. are all possibilities and would make for a much better variety and less of a dull monotonous hoard at each dungeon, delve boss, world boss and dolmen.
I know it's more work for you, but in the long run, it would be more fun and more eye appealing. And, you can apply this to future events where each time you drink/activate the event item you get a random polymorph into a related creature.