Thanatos card does work properly. It's simply an improved goldenring effect for champs. This is why people claim it doesn't work for tss (it doesn't stack with double fbh, just like goldenring). However when you compare asuras the right way you will notice thanatos having slightly higher damage for regular asura. Just remember that when you use thanas in your weapon, you'll have to switch weapons if you want tss to be effective.