I'd suggest removing vouchers and making cards more profitable to burn than DEC. As of now doing the math, I think this would basically burn a lot of reward card over supply and vouchers. I also think some sort of promo card would really increase the desire to participate, something like a vruz where pretty much anyone at any level could reasonably qualify to get a copy.
RE: SPS Governance Proposal - Hire Steem Monsters Corp. To Build Card Burning Event & Provide Riftwatchers Packs as Prizes