It used to be. But it was very difficult to get in the slots (refresh dozens of times), and then it would drop about once every 200 capsules or so. That's the only experience I had with it.

Now, it may not even be possible at all anymore, because they recently added completely useless ninja like Minato Jonin to the slots. In doing that, they probably took away ninjas that made the event worth participating in, like Pain.

I agree that disclosing this information AND bringing in worthwhile ninja (not just Pain) would make this event worth participating in again.