I personally think the rune is cool, but slowing effects are not as efficient in the game anymore. And there is not enough items that can make use of it, to justify taking it.
Will there be any possible improvements for it towards the future? Maybe in the form of additional items to make use of it
Funkin Dunkin1 votesIt's a good keystone, but it's in a trash set of Runes. I think that's the major drawback of it. I use it on 1 or 2 of my champions and it does very well. But its very niche specific.
TheDangerousTaco1 votesyea that's the problem I have with it as well. I tried it on sivir 
. It worked pretty fine, but I found myself preferring just raw damage or attack speed instead, with arcane comet or even fleet footwork. So its sad to say, but even on those good champions, there are just better keystones overall
Trash MammaI1 votesPretty much only bard can use it well
Existential Bard1 votesIt's really good on A LOT of champs. Just have to be creative. (Aurelion sol, teemo)
TheDangerousTaco1 votesNever heard of sol using it, but I guess that would make a lot of sense, since he primarily builds glp 
Woodakoodashooda1 votesSlows are incredibly effective.
What isn't effective is having a Rune that does the job of other champions, but does it so poorly that picking it over a champion already with a slow built into it is counter intuitive.
TheDangerousTaco1 voteshmm I can see your point. It also works similarly to frozen mallet, which I found counter intuitive. you might as well get FM
instead of the rune, and just run attack speed instead
Sire Hippington1 votesine big issue i have with it is that it requires items with slow actives in order to really use the full potential. If the slow field was either triggered by any slow from items or by any item active but with an internal cd, it would be alot more usable. It might be interesting on someone like garen if if it worked with the deadmen's slow proc or with yomuun's active
The main issue however is that other runes offer so much combat power that going for a no combat power rune is a massive setback, atleast for laners. it doesn't help me if i can force fights and stick to targets if i'm not able to win those fights. Phaserush has a similar issue, it's not a bad rune, but other runes offer so god damn much damage that you can't really afford to not take them.
TheDangerousTaco1 votesIf they made it active on items like redemption, I wonder if that would make it too strong. Then again it would probably make it more unique in the aspect that supports would pick it just for more peel potential
sadaiblast1 votesI made an entire forum post on this that maybe you could read and see if you get any ideas from it.
anyhow maybe reading this would give you some ideas and thoughts on what could be done on it (make sure to read some of the comments and discussion too as more of my info is there too.) anyways rather than making a long discussion here i thought maybe you'd like this and get some thoughts from it :)