Nostalrius Begins - Quality wow vanilla realm (1.12)

So I picked up Curse of Exhaustion and put 1 point into the improved version.

Can anyone confirm if this actually works?

I ask this because it still reads at 10% slow instead of 15% slow when casting it on mobs.

improved curse of exhaust does not work.

Improved should work, but amplify on it does nothing.

Thanks for the reply's. I've opened a bug report on it to try and get some clarity.

General Update:

This is the reply I got after submitting the query via the bug report.

"The extra slow effect is working, The tooltip does not currently change though."