The Morde 6.1 changes are step in the right direction, but there's more that can be done
Being able to W minions is a great feel improvement and significantly helps his laning. He has another way to get last hits from a distance or push the wave without getting too close. There's still one thing I don't like about his W though: the passive. Bonus XP feels negligible unless it's enough to give a level advantage, which in most cases it doesn't right now. Since this passive has been shown to be too overbearing when it works well, it'd be best to just remove it and give Mordekaiser power elsewhere.
To couple with the change to his ultimate, an AD scaling on his W damage and heal would be an excellent addition to his kit. As it stands, trying to venture into AD or hybrid builds leaves his W feeling rather weak as you don't rank it up until last. And even when you do build AP most of his W's power is in the base value, which again, isn't great since you max it last. If AD or hybrid builds are to work his entire kit needs to benefit from them.
that can be done