@ Riot, net effects of Vel'Koz changes:
TLDR Summary: You took a champion that everyone liked and, in an effort to more "clearly define their strategic identity:"
- Reduced the coherence of his itemization
- Reduced the coherence of his kit
- Reduced his teamfighting potential
- Increased his single-target damage (despite literally EVERYTHING in his kit being an AoE skillshot)
Explanation:
Single Target Damage: Vel'Koz typically lanes against either botlanes or midlanes, neither of whom are likely to acquire significant MR until mid-game, at soonest. Vel'Koz deals significantly lower damage to low-mr targets in the early and mid game. Late game, single target damage is improved ONLY if you land a full combo. The "late game tank shredding" fantasy he has been forced onto does not occur until late game.
Multi-Target Damage: Weaker at every stage of the game, significantly more-so early than late.
Item Build:
Before, a combination of high base damages and relatively low AP ratios meant that magic pen was far and above the best stat on Vel'Koz. Picking up an early 
was a great way to do excellent damage. 
gave you similar power while giving you the speed an immobile kiting mage desperately needed.
Contrast this situation to the live 6.9 changes: the lowered ratios on W and E have more synergy than before with magic pen, but the ap scaling true damage on passive and the possibility of having a true-damage ultimate is now better with flat AP. His abilities are now at odds with each other; if you can proc your passive on a target, raw AP gives MUCH higher damage, while if you can't proc passive (for example, hitting multiple targets in a teamfight), magic pen gives better damage.
Itemization now feels like a lose-lose for Vel'Koz players.
Passive: You intended to make his passive feel more important and have more impact. What you did was make his passive proc for more damage, less often, and now gates his ultimate.
Ultimate: The ultimate now feels much worse. It takes at least half the game to acquire enough AP so that it feels like it does the same amount of damage it used to. Optimal use of his old ultimate was to deal as much damage to as many champions as you could. Optimal use of his new ultimate is gated by procing passive first, which is often only on a single target. Focusing a front-line tank to death is rarely the right call in a teamfight, even if he can do it by channeling a full ult. The new ult has poor synergy with the timing of his CC.
Please consider this thread and others like it. We may be a "vocal minority" of the community, but, when dedicated Vel'Koz players are a small minority to begin with, we represent a larger portion of the Vel'Koz loving community than it appears.
