There are very few champions but there are some, like 
, where sometimes the slow was the necessary tool to help an ally secure a kill. But instead of an assist, all we get is a crisp high five for it. I feel like that's not very fair. Even if you're not damaging someone it is still contributing if they are affected adversely.
Professor Ward5 votesAs a support main, non damage assists already exist for 100% fact, im not entirely sure about slows, and singed specific but
Exhaust=assist Any shield on ally = Assist Any speed boost on ally = Assist
Funkin Dunkin1 votesBut it doesn't give singed an assist because it is not a point and click slow. With exhaust you are physically clicking the champion. His slow is an Area Ground that doesn't specifically target.
undesirable team1 votesyes it does lol. anything that a champion does to another will count for an assist, even a 
w will give an assist..
Funkin Dunkin1 votesWell then Singed W is bugged and needs to be reported to the bug forum if that's the case.
Zero Skill Tank1 votesI can confirm what KennyLay said. You don't need to do any damage to the enemy champion to gain an assisst. If Singed W doesn't grant assissts, you should report that as a bug.
If anything, the system is too permissive, i.e. attacking someone while blinded will still grant an assisst.
Funkin Dunkin1 votesI've already reported the bug
Sona Ping1 votes"Give us assists for non-damage skills" That is already the case. In fact, the bar for gaining assist credit is incredibly low.