Alliance roulette to encourage Crystal Tower participation is a great idea. Take my like!

Extreme roulette to encourage Coil or Ex Primal participation could only work if the rewards system was massively revamped for that particular roulette. Because several of these instances would have a high failure rate, there would be need to be significant rewards for ATTEMPTING the instance, not just for completion, or folks will bail rather than even try. Or worse, not use the roulette at all. Something like, stick around for the full duration and get fully rewarded; stick around for 40 minutes and get mostly rewarded, stick around for 20 minutes get half rewarded, less than that no reward at all. Even with that, the reward would need to be pretty big to get folks interested.