Personally I don't see the point, this isn't going to do anything except take away options in the future.
It's not going to change the short term supply or demand for these cards since they aren't on the market, delegated or otherwise available to any player. So no near term improvement in CL market dynamics. It's just a "It feels good to do something" proposal...

Personally I think anything that gives the DAO options is a valuable tool in the toolkit. And since burning means that we can't ever make them available in the future, if the situation ever changes... then burning these means the DAO will never have that tool. I generally prefer "giving to DAO" over most burning mechanics.