Yes, it is, and it’s not the only thing that’s broken/bugged.
- Time Anomaly.
- Clearcasting / Arcane Empowerment (CC bonuses only for 1st in stack).
- Blink.
- Charged Up (sometimes only 3 charges, because of out of combat decay overlap). and Time Anomaly when it worked.
- Clearcasting and Slipstream (sometimes need to stop on proc and then run again for it to work)
- Brain Storm trait doesn’t proc Rule of Threes
Plus other messed up stuff and bad changes, no improvements.
But hey! At least Arcane Orb works a lot better.
Since it’s a holiday time and half of bugs are not fixed since pre-patch (years for blink) - I guess Arcane is left in this state for more months, and there is no point hoping that it’s going to be fixed soon.
Edit:
Thank you Blizzard! Time anomaly fixed in Patch 8.1 Hotfixes for December 19th
Clearcasting / Arcane Empowermen bug also fixed, but not included in patch notes.