Syndra's ultimate has always been able to do a lot of damage. Only with the MYMU update can she have access to maximum dmg at level 13. The nerf/revert to her W will only make it to where she can grab one orb, like before the MYMU. Pre MYMU her Q lasted for 6 seconds, and she only needed 35% CDR to access to maximum dmg with her ultimate.
Now, her max rank Q's last for 8 seconds, and they are not reverting her Q back to 6 seconds. This allows her to get 7 sphere ults much easier than pre MYMU even after the revert to her W.
They are increasing the CD of her ult (not neccessary), and reducing the dmg of her W by 10 I believe. Her W will have 20% true damage on it as well.
TLDR: The revert to her W will only allow her to refresh the timer on one sphere and she will still have access to max ult dmg and AoE stuns due to the extra 2 seconds on her Q's. Increased CD on Ult, W nerfed and switching base dmg for 20% true dmg.