Something with a super cool cop, with romance.  Would prefer a female lead that isn't a cop but something like "when a snail loves" is alright too.  But the male lead has to be super cool and a cop.  Really want something like the cop in healer, but about him.  Healer is suuuper cool.  But I want a cop now :P  If there's nothing quite like the cop in Healer than that's alright.  Alright, well thanks for the future recs :P

I would say Signal since the best cop in kdrama land is Lee Jae Han. But romance is not very strong here. 

And if I am not wrong Seo In Guk is a cop in Hello Monster...(?) Jang Na Ra is his love interest there.

Taiwanese drama the Masked Lover. The ML is a cop who leaves the force in order to go on a personal undercover mission to expose the mob boss responsible for his informant's death. However, the mob boss is targeted and gets into a car accident that puts her in a coma. Her twin sister, an architect working abroad, secretly has to take her place

It drags a little bit in the second half and it's definitely not the most serious cop drama out there, but if you're just open to enjoying it as a light rom com with a bit of action, it's worth trying. 

Edit: I'll second Hello Monster. It centres around a team of criminal profilers / detectives (similar to When a Snail Falls in Love) pursuing serial killers.

Since you've watched I Hear Your Voice and you're watching W, I also recommend watching While You Were Sleeping. Lee Jong Suk plays the male lead, a prosecutor whose father was a cop. The second lead (one of the greatest second leads ever IMO) is a cop. He and his partner have a pretty big role in the story.

You might also like City Hunter. A lot of people describe it as a darker version of Healer. The ML is a security agent pursuing a revenge mission. 

Scandal is a korean drama. The male lead is a cop and the female lead ended up working in a lawyers office.. It has romance part though not the mahor narrative factor of this drama. The story mostLy revolves around the male leads life, work and secret birth

missing you or I miss you where the ML is a cop or a detective and FL is a designer

Lovers in Prague an old drama where he is a cop and she is a diplomat. One of my fave kdramas ever.

Time between dog and wolf where the ML is not  a cop, but he is an NIS agent, koreans equivanet to CIA. But he tasked to take down and investigate gang/triad organization.

While You were Sleeping, though he was not a cop, he was a prosecutor. Somewhat same type of work with trying to get bad guys. Plus they have a super adorable and awesome cop character in the drama. 

There is another drama where the lead is a police but it was set during the japanese occupation of china, so being a cop actually means they are considered dogs of japanese empire, but he is actually an undercover freedom fighter. Same the girl. Its titled Bridal Mask

I also agree woth Hello Monster, though the female lead is also a cop. Same with the korean drama Posiedon, You are all surounded, HIT,

Black & White - taiwanese police drama that not only has 1 cool and handsome cop, but two handsome and coold cop in Vic Zhou and Mark Chao

there is another drama i wanna suggest, but its a different type of drama but probably the best among the ones i recommended. Anyway just check out Heartless City

You're All Surrounded- Both leads a rookie cops. They're not that cool for the first two episodes but they get a lot better. 

Black- The ML is a grim reaper that possesses the body of a not-so cool cop, after the possession he becomes badass. 

King2Hearts- The ML is a king but he's also a trained soldier, the SML is a trained soldier/bodyguard and they are both smart and cool. The FL is a trained assassin/soldier as well she's more badass than the guys. 

Suspicious Partner- He's not a cop but a prosecutor. In SK they do their own investigations so he's almost like a cop in that regard. FL is a rookie lawyer. 

The Girl Who Sees Scents- He becomes a cop after his sister's death in order to be able to solve the crime. He gets really good at solving cases with the help of the FL.

The K2- He's an ex-soldier that becomes a bodyguard. Same lead from Healer which you seem to like and from Suspicious Partner. There's no wrongs when it comes to Ji Chang Wook.

Who Are You- He's a cop that is really good at shooting and fighting, she's a cop as well but she can see ghosts after waking up from a coma. 

I've just realized that I've seen lots of cop dramas xD