So, let's talk about the Mordekaiser Rework, shall we?
For those of you who haven't seen it already, I linked it.
So, we will now look at each abitlity individually and analyse his updated kit in general.
First off, his passive: It hasn't changed that much, the shield no longer decays at 25%, which means you will always at least have a 25% shield (as far as I understood it). The decay rate over 25% is now 2% of max. health, no longer 3% of the max. shield, which I think is a nerf because your max. health is far bigger then you max. shield, the 1% difference doesn't really matter, also the shield now scales of 25% of your max. health and no is no longer based on levels, which encourages a tankier build in my opinion. Tl;dr: Bigger shield, faster decay rate, always at least 25% shield (when you take no enemy damage).
Then his Q: It now no longer "splashes" to other targets like before, it now** amplifies bonus damage on the next 3 autoattacks** (So on the third auto, tripled bonus damage) This may sound like a huge nerf, because you now have to actually hit you target and not a minion (for the splash) to deal damage to your target. And I think it's actually a nerf for the early game, because you normally don't walk up very close to your target for the Mordekaiser poke. It encourages a tankier build because you can't "range-poke" with your Q anymore, also they buffed his HP, HP Regen and all those stats to make him tankier, but the damage in mid and lategame is very good because it triples a fixed value of bonus damage, which will be very high on the third hit (if you land it, that is) Tl;dr: No splash anymore, now bonus damage that gets amplified up to 3 times on the third hit.
Now his W: Almost the same, but also in my opinion his hugest nerf. He can't cast his W on minions anymore. He can only cast it on allied champions, but it now deals quite a bit of damage and you can reactivate it to heal you and you allied champion for a bit of the damage dealt, you also get 75 Movespeed like before the rework. Also a new passive: Mordekaiser gets all the experience of minions he killed. You may ask yourself now: "What? Why did they add that? Mordekaiser is a solo-laner, he doesn't need that passive!" **And that's exactly what I thought too, but then I realised: They want to make him a ADC/Support. ** Don't ask me why, I don't know it, and I won't explain it to you, but I hope Riot let's him cast it on minions again, so that you can play him in solo lanes better and I really question the decision of Riot making him a bot laner. Tl;dr: All the same, but reactivate for a heal, can't cast on minions anymore, more of a bot laner direction now.
Coming to his E: I thought about it a bit, and did a bit of math, and I came to the comclusion that it is a buff and not a nerf as I thought earlier. So, the only changes: Base damage lowered to 35 from 70 at Level 1, BUT now scales with both 60% AP **and ** 60% AD instead of only 60% AP. This encourages to build Hextech Gunblade instead of Will of the Ancients (in my opinion, please don't flame me for that idea), because you know need extra AD too, which is a good thing, the enemy has to buy Armor and MR to counter your damage and you do more damage with your E overall (this is from a solo laner perspective, I don't like the bot laner Mordekaiser idea of Riot as you may noticed earlier). **Tl;dr: **Now scales with AD too, but lower base damage.
Last, but not least, his R: First off, a new passive, if Mordekaiser damages the drake, and then his team killed it after 10 seconds, he gains a ghost of the drake. That itself is very nice, because the time that the ghost is there was also increased to 45/60/75 from only 45. The best thing is, the ghost of the drake does not affect your ultimate cooldown, you don't have to cast your ultimate on the drake, as it is a passive effect of the ultimate. The problem is that they reduced the damage from 34% to 30% of max. health at Level 3 and the ghost gets less bonus AD. And you can also see the bot laner direction in the new passive, as I think the bot lane has more drake control then a solo laner, because the drake spawns near them and they are faster there when the drake spawns as for example the top laner (without using Teleport). Tl;dr: Cool new passive which lets you have a ghost of the drake for free, ghost duration buffed, but damage and bonus AD for the ghost lowered.
Finally, my conclusion: I think they buffed Mordekaiser in many aspects, but he has a huge nerf to his Q, because he now has to walk up to his targets and hit them (and that's difficult with no CC and no Mobility (in a solo lane where he cannot cast his W on minions)), his E and R are buffed, that is good. But I really request Riot to give him back the ability to get at least a bit of Mobility without being in a duo lane and let him use his W on minions. All in all Riot should get away from the bot lane direction they forced Mordekaiser in and consider the solo lane Mordekaiser more. Tl;dr: Change his W to how it was before, but keep the heal, and maybe give him more Attackspeed for the duration of his Q to actually land the third hit.
If you have any more questions or feedback for me, you can post it in the comments, I will try to respond to most of it.
Greetings, Salmighty
EDIT: Removed the 600 range on the Q, that is misinformation.