TDE has existed for a while, and is certainly not fixing these things for us InfoSec folks. https://www.oracle.com/technetwork/database/security/tde-faq...

There are a LOT of companies that can't run that, since it requires Enterprise Edition of Oracle.. That is a huge jump in price over standard edition, even for most larger companies.

I don't see how encryption at rest helps with an online attack.

Once the file system is mounted the filesystem is unlocked. This is way things like LUKS which has bee around forever work today.