Vel'Koz alone can cause a big meta-shift that some should love
Vel'Koz is transforming into the ultimate tank-killer mage. Thanks to his true damage, he will destroy tanks that primarily build tons of defense.
I remember a lot of people complaining about tank supports (especially Alistar) being too present. Vel'Koz will destroy Alistar through his ult, Braum through his shield and Leona through her defenses.
(I'm a tank support main myself, btw, but I like these Vel changes)
And for tanks that build health rather than defenses, we have Brand.