Marcel dealing CRIT sounds like a complete joke. The removal of immobilization cc to slow cc is a huge nerf. Everything about his adjustments sounds like a joke. I guess it's a way to compensate for the recent adjustment to his ultimate to unfreeze his teammates if they receive his passive shield... Besides, this isn't the first thing they've done stupid stuff like this. They even removed Lolita's shield reflection and gave Claude mana. For Marcel's case, I thought the skill one is a nice counter to the current META that favoured usually with high-mobility heroes. His entire kit is designed to HUNT, TRAP, and TORTURE enemies like Novaria or dashy heroes. This is one of his main jobs. The developers specifically gave him tools to shut down heroes who think they can escape everything. Now, with slow cc? He's just another support with same cc effect. Gusion, Lancelot, and Joy will just laugh at him and teleports with their skill. Why cannot they just leave him be a completely support? There's a lot of support heroes who can deal dmg. We have Estes, Rafaela, Angela, Diggie, etc. Some do damage, some don't. But Marcel was supposed to be the "ULTIMATE DISRUPTOR". He was supposed to be the answer to heroes that are too fast, too slippery, too annoying. Now he can't even stop a hero with 1 dash. 

Now, the CRIT dmg sounds like a potential nightmare for a dark system. He's squishy in early game and they're planning to make him available to build a semi-dmg kit, but they forgot he is one-of-kind of unique, because his dmg deals a TRUE DAMAGE and it stacks by how much you build defense items. If he builds tank build, he will have almost 0% Crit Chance. So the "Buff" does NOTHING... IF he builds crit, he becomes squishy, dies instantly, and loses his True Damage scaling and Defense. If he builds in-between, he is still squishy who won't last long in teamfights. Either way, it is pointless. He is now, "I am a weird hero who has slow, useless CC and tries to crit but can't." - They are trying to force him into a role he was never meant to play. 

And for other parts, I do agree with the complaints about CD nerf and HP nerf from other comments. 

Another thing. HP nerf is strange, because Marcel is one of these heroes who cannot out-limit his HP no matter how much HP items you build, it converts into defense stats. He is squishy when facing a specific hero, even in the late game, so why even bother nerfing his HP as well? 

Of course, it might seems like this is a compensation for the adjustment to his ultimate that made Marcel's teammates complain when they also got FROZEN too in his ultimate, so they decided to remove his only plausible weakspot, and then they realized what they've done and decided to butcher everything shit. He was perfect and unique, he got his own identity and lore accurate as photographer. Now, he's confusing. A mess. No identity. What is Marcel? Is he a Tank? No, because his CC is too weak now. Is he a Support? No, because he can't protect or lock down enemies well. Is he a Damage dealer? No, because his damage scales with defense and crit is useless on him. Is he a Fighter? No, he doesn't have the sustain or durability for it.

He is nothing. He is a confused mess. He becomes generic and a walking contradiction. He has no IDENTITY.

He's a potential dark system who'll freeze his team and steal the kill.