Jhin gets a small ms buff when he hits his 4th ult. But its barely noticable.
Personally I find Jhin's combat stats fine. He hits hard, and has a drawback that is not ignorable. But the only thing that bothers me is that using his ult far back and then going back into a fight is real hard. He is just darn slow. He gets this movement speed buff when he hits his fourth ult, but its really unnoticable since he unfolds his gun and the duration ends. Jhin's combat theme is all about fighting at the right moment, and I sorta think he needs something to make him arrive on que which fits his theme.
So here is my idea.
Ult passive: Red carpet When Jhin lands his forth red ult it leaves a faint red trail that Jhin can walk on, which raises his movement speed gradually.
With this Jhin can pick enemies and then go in his favoured fight with more ease and can also traverse backwards on the carpet so he can kite better.
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, you'll pretty much get it on every shot AND move really fast. Also, your support can build
, increasing the chance of activating it further periodically. It can actually get pretty crazy.