I had to make a post specifically to address this, because pre rework tendrils is just busted.
The cast time on tendrils did not take into account the animation timing, and so cast speed didn't actually result in recasts at the suggested intervals.
I went from storm burst to lightning tendrils because paper DPS was about 4x as high, but in the end simply swapping out tendrils for ball lightning with paper of 50% of tendrils did observably more damage, with more area, and without animation lock.
I don't know how the rework addresses this but lightning tendrils, before 3.1, is basically broken. If the cast and animation times are synced with the new version, it's an automatic buff, before the fourth pulse bonus.
I cannot stress enough how bad the spell is currently. Ball lightning only loses to it if you are doing area damage scaling. Even in the hit count, lightning orb is higher. And since they are both low damage multi hit attacks, I don't think even shock comes into play.
Whatever 6L has tendrils in it, swap ball lightning and switch a gem for slower proj and you will always do more damage because of the animation timing on tendrils.
With channeling, there should now be a 1 to 1 correlation between pulses rate and cast rate.
It does lose echo, but I imagine the animation timing fix will actually result in a faster actual cast rate with increased cast speed support over current with echo.
tldr: tendrils got a huge buff if this fixed the animation timing.