Imma speak my mind, since that's what this is for and I played all the juggernauts (yeah, even Skarner) way before they were cool.
Alright, so let's do this.
Darius - In my opinion, he was a little weak before. Sure early game and squishies got smashed, but then he really couldn't do that much. The only thing I like that they did to Darius was his new passive, since getting all 5 stacks off every champion was kind of a pain, and the ult-minion-fear-thing because I think it's hilarious. However, his hook getting a slow was unneeded, his Q healing was okay (but I think it heals way too much AND it now has a cast time so his old combo no longer works) and his passive giving him so much bonus AD is ridiculous.
Garen - I think his fine, actually. He needed something, anything to boost him in game, and now he targets people who last got the kill, who might be really fed, so he can do true damage. However, I do think he does a little too much and maybe instead could do, like, less or bonus AD or some random magic damage (idfk).
Morde - Eh, his Q does a metric shit-ton of damage on third proq, but other than that I think he's fine. He's back in the meta with a brand new kit (ish) and has a Dragon. He just builds weird and goes bot or whatever now...
Skarner (And this rework is actually my least favorite) - So, the new passive is kind of stupid. Not in the broken way, in the bad way. His old passive made much more sense (and not his old OLD passive or his old old OLD passive, cause Bard knows how many passives he went through) hitting them with damaging abilities to then stun em for a time. Now, his E proqs his old passive alone, slows more, and his Q is basically just for some little bit more damage. His W is, well, there, and his Ult is the only thing I liked that they changed, since now he gets move-speed and can run away with someone (which is why everyone had something to give them move-speed before, like Talisman or Yomuu's or something random). But his Dominion is silly. It's very situational, so unless you fight in that space AND the enemy team hasn't captured it, you basically run out of mana and can't really anything. Sure it's a unique passive they gives him a unique play-style or whatever, but really, he already is unique, considering he's a Scorpion from an extinct race that can move a champion at his will with one button.
That's my two cents, fam.
And
cigar joke, blablabla.
~Bubbles