How is Mordekaiser supposed to Compete Against ADCs?
TL;DR: Morde cannot catch and keep up with ADCs long enough to hit them three times with his q. He either needs some form of slow/grounding combo spell or reduced time to deal his Q damage, or a combination of these two options.
Mordekaiser's most recent rework was geared towards making him a bottom lane "Juggernaut." My question is simply a rephrase of the title. ADCs are weak champions who do a large amount of damage very quickly. While their defenses are weak, their ability to move around the battlefield with abilities more than gives them an edge in avoiding damage. Now, you mean to tell me that an (approx) 8ft high spirit clad in heavy metal can catch these hyper mobile, hugely destructive glass cannons? Ok.
Your first response to this might be "Well he needs to coordinate with his support to effectively secure the kill." This is a good point. For this example lets say everyone in bot lane is level 4, and Mordekaiser's support is Leona. In this example we will say the enemy support has one spell that is hard CC (stun, knock-up, or knock-back). Leona will attempt her E+Q combo and stun the adc. Even if Morde has his W on her, Leona's stun lasts 1 second. Morde cannot close the gap to begin his three-hit combo in one second, unless he flashes or uses ghost. Even if he did land the first hit, at this point the ADC escapes the stun and has used some movement enhancing ability or the Support with one CC ability has applied it to Morde and interrupted his three hit combo (the active time on his Q isn't very long, at least a second) and his Q becomes inert along with the potential for a kill.
"What about Rylai's Crystal Scepter?" A 2600gp item isn't affordable by level 4 or even level 6, even if it was rushed. Even if it was relevant, Rylai's only slows movement speed, and only for a second. Vayne can still tumble away (and apply a knockback, further widening the gap); Ezreal can still blink away; Caitlyn can still 40cal Net away (while applying a slow of her own, by the way); Kalista can still short hop away (the slow only lengthens the duration between each hop, not the distance of the hop). Not to mention, Varus has a slow, Ashe has a slow, Miss Fortune has a slow and a movement speed buff that she can reset by activating her W, and Jhin has a slow if he dupes Morde through a trap (said slow evolves into a snare if he's auto-attacked by jhin again). In short, Rylai's Crystal Scepter an expensive item that Morde must by to even try to fit the role Riot shoehorned him into, is irrelevant. "Well, of course Morde is gonna take damage getting kited by ADCs, that's why Rito gave him a heal with his W." Ah, I see, a heal. This heal must be activated after cast or Morde must wait 4 seconds. He goes in on someone and activates his W. Any support worth their salt would have already CC'd Morde for his audacity. Now Morde is getting battered by the enemy ADC. Morde cannot emergency heal with his W to mitigate the damage, he has to wait until the CC is over. Also, the Heal only fully procs when it hits an enemy champ. He gets reduced healing on minions and it only procs against a maximum of two targets within the AoE. That's gonna have to be one minion and the support, I guess, because the ADC is leagues away from the AoE. If Leona has managed to stay on the ADC, she'll get the heal, but not Morde, the lion's share of the damage in this fight. Another reason why Morde can't catch and kill ADCs is because he is inherently slow. Possibility of Morde getting CC'd aside, he is just unbareably slow.
How can we fix Morde as he is? Well lets look at his Q. Yeah, his Q does a lot of damage on the 3rd hit. Remember, He cannot keep upwith most ADCs let alone hit them. In addition, at level 4, his attack speed is only .63 attacks per second. If Morde manages to fight through getting CC'd and catching up to the ADC, he only has enough time for 1 attack. Riot wants him to make three. Ok. Why can't Morde have his old Q, where he just smacked someone really hard? He doesn't even need his old Q back entirely. He only needs one powerful auto attack. Give it a longer cooldown if you must, but at least it will give him a good trade opener as well as some shield up front (or at least returned; I am aware his E is supposed to be his prelude to slaughter). Having a character who is inherently slow, needs outside sources of CC, and a 2600gp item to just hit a hyper mobile glass cannon once is deplorable. By the way, this is assuming he doesn't get CC'd after activating his Q. In short, Morde's Q needs to deal more damage, but only in one hit, like his old Q. It doesn't need to damage other enemies like the old Q, but it needs to be more effective than it is now.
His W also needs to be reworked. A heal is nice, but that's what spell vamp and potions are for. Morde needs his Armor back on his W (15/20/25/30/35) or (10/15/20/25/30) if you feel the previous listing was too generous, but remember, he is supposed to be a juggernaut, and he doesn't have his heal anymore. That way he can protect himself early game when he's rushing Rylai's for a time, and still protecting himself from the ADC's damage, rather than relying on the dream of healing himself off both enemy champs. By the way, Armor is passive, so it gives Morde hope while he is getting splashed by amber waves of hard CC. You can take away the MR component his old W if you wish, if it means he can get more armor early game to resist getting shredded.; Morde's an ADC hunter now. The four second duration is still good as well. Here's how Morde is going to catch ADCs. He can put his W on enemy champions. Instead of getting armor and a DoT by applying it to himself or an ally, He can place it on an enemy and ground them, while at the same time stealing a percentage their movement speed and adding it to his own. Magnets attract metal right? That was the reasoning to adding the movement speed buff when he applies it to an ally? In summary, here's how this proposed W would work. He can buff his or an ally's armor. If he buffs the ally's armor, he gets a percentage of the ally's armor as a movement speed bonus ('cuz magnets, bro). In either case, the W would apply a weak DoT, soRylai's could proc. This Configuration would last 4 seconds. The second configuration would be applied to an enemy champion. It would apply the Grounded status effect to that champion, and steal a percentage of their movement speed (15%/20%/25%/30%/35%). This configuration would last 4 seconds as well and deal no damage to either the ADC or the surrounding enemies. It would give Morde the ability to catch up to the ADC and prevent the ADC from widening the gap with their abilities. On the flip side, it would give Morde a means to escape should an encounter go wrong ('cuz magnets, bro). If Riot wants to give him powers of magnetism as well, Morde would want to leverage them fully. This also gives the player a choice to either make himself more resilient to damage or ensuring he can catch his kill. His Ultimate is fine. I have no problems with it.
In Conclusion, I feel that these changes to Mordekaiser would level the playing field in fights against hyper mobile ADC (which seems to be a lot of them), while still making him an "unstoppable juggernaut" that Riot wanted him to be. He would still be slow, without an enemy champ to leech off of. He would still be susceptible to CC. He still needs to deal damage in order to get his shield (temp HP).