Compensation For Rylias Dependent Champions
Based on what I have read it seems very likely
will become a mana/cdr item similar to
. If this doesn't happen the other route that was considered and suggested was lowering the slow amount on it. Either option does not suit three champion in particular
,
, 
Sure Karthus and Singed would not mind the mana portion on the change, but the cdr stat is not something that is usually built on them. Champions like
or
would benefit even more with this change and all the would lose is the health portion. Karthus NEEDS to build health or he gets blown up quickly and he needs the slow since he does not have reliable cc ( even less so with the Nerf on his W). Morde and Singed also need the health portion on Rylias since they don't do burst damage (Morde does with only Q) and do well in extended fights.
If it comes to a point that these champions are worst because of the changes on Rylias it is your job Riot to compensate them like you did with other champions and item changes. When
was changed, champions who used it were given changes too to neutralize any draw backs. When DFG was removed, champions across the board were changed to help compensate the loss. So if Rylias were changed it would only be fair that you change champions who rely on this item the most like giving them built in or better slows on their kit.