The MYMU changes made Vel'Koz way too situational and binary

Riot planned to make him have his own niche and give him more thematically fitting gameplay, without changing him too much, since he was pretty much the epitome of a balanced and fair champion. The goals were achieved, no doubt about that, it fits the research thing much more and also gives him (kind of) and identity as a tank-shredding mage. In reality, the changes feel rather bad to play. His ult can be really strong (the true damage is absolutely insane), but his reliability is now lower than before, much lower. Before the update, in late game you would look for a good opportunity and especially a safe position to land a good ult. Q and E were basically only for peeling off nasty assassins and bruisers. Now, in order for your ult to do true damage, you are forced to land your E, since nobody with half a brain is ever going to get 3 stacks in a reasonable amount of time without getting hit by the E. So, on top of positioning yourself so that you can channel more than 1 second without getting jumped on, you have to land an EW combo on the enemies to actually deal reasonable damage, which puts yourself in a really dangerous situation. Meanwhile, if you randomly land an E on an enemy, he is pretty much dead instantly if you have your ult ready. The other changes were quite unnecessary (he never had problems with mana or damage).

I liked playing the tentacle dude a lot, he was one of my favorite champs, but he just doesn't feel right anymore. His whole kit is now centered around hitting his E; if you hit it, they're dead, if you miss it, you're hardly useful and probably dead, too.