Even 
now seems to be a much better slowing option when paired with Glacial Augment. Rylies just seems outclass in every way now. Both in stats and its passive.
Might as well remove the item at this point.
Imperial Pandaa3 votesExcept 
applies a slow with every ability hit. It is less about bursting and more about chasing/kiting. I'll be able to trigger Rylais again sooner than the CD for .
The reason why Glacial doesn't work with it is because Rylais is a passive and not active.
xxxMadLionxxx1 votes[{quoted}](name=Imperial Pandaa,realm=NA,application-id=3ErqAdtq,discussion-id=YGUJeWtP,comment-id=0000,timestamp=2018-01-26T17:22:37.000+0000)
Except
The reason why Glacial doesn't work with it is because Rylais is a passive and not active.
I know why it doesn't work. I'm just saying the slow from rylies is kinda useless in general because its so weak
Mig891 votesIts not weak, its just not OP anymore and is a situational item. I like it because its on the cheap side and I play support zyra. Every plant slowing helps tremendously in peeling and catching picks. When couples with liandries it makes her plants do a solid amount of damage and since there are so many hits the Mpen from liandries gets a ton of damage off when coupled with the enhanced burn from enemies being slowed. I hit a power spike earlier because i dont need top dollar items.
Imperial Pandaa1 votesIt really depends on the champs.
Minion users can get a lot of benefit out of it
(Mainly because Annie might prefer protobelt.) Champs that have wide area spells get a good boost too.
Ones who have majority skill shots can also.
Is it core for any of these? Some is rec. There are also others who do well with it (Vlad because of his passive.)
If you stick with the focus on glacial augment then you are probably correct.