Rawr...so I'm in a drama slump. I'm getting tired of ditzy, clumsy, ineffective, candy girl leads and am looking for more flawed but fascinating STRONG female leads in dramas such as "I Can Hear Your Voice," "Witch's Romance," "Protect the Boss," etc. I strongly prefer rom-com, however I'm aware that I probably should open my mind to other options :)

Divorce Lawyer in Love, History of the Salaryman, She is Wow! (it's funny, but not exactly a rom-com), Ugly Alert (long one, but with really awesome characters and couples), The Woman Who Still Wants to Marry.
Not necessarily rom-com's but all have strong female leads from what I can remember;
All about my romance
Dae Mul
Empress Ki
God's Gift - 14 days (no romance)
I Do, I Do
Warm and cosy
King2Hearts
Ms. Kim's Million Dollar Quest
I would defenitely recommend Angry Mom, Kim Hee Sun's character is really awesome! Also, she plays a pretty strong character in Faith too. :)
Thank you so much for replying :) These look awesome! I'm really excited.
Murphy's Law of Love
I Love Lee Tae Ri
She's On Duty
Noble, My Love
I second Angry mom. It's one of my favourite dramas ever. I loved every bits of it. And it deals with actual problems, but it's still funny.
I recomment The New World it's a Taiwanese drama. I've just finished watching it.
The female lead is quite awesome in her own way and she tries hard to not appear weak or vulnerable. And there are other female characters with strong characters and qualities.
The story has flaws and it would have being considered makjang if it was Korean but I found it super good enough to watch all the episodes in one day. 

I've watched over 200 dramas and my memory goes crazy when I try to remember more. Sorry.

falling for innocence is a really good one. I loved how competent, smart, and capable she was. 
Capital Scandal has two strong female leads and is primarily a romantic comedy although it has more serious elements as well. While they aren't rom coms, H.I.T., Secret Love Affair and Incomplete Life have strong female protagonists/or or major characters. If you're okay with a long historical, Queen Seondeok has both a great female protagonist and an even better female antagonist.
I recently finished Akumu-chan and thought the lead was very well written, definitely not candy girl. There is more comedy than romance and sometimes its a little bit scary but I would recommend it
Arang and the Magistrate. It does sag in fiesty-ness in the 2nd half, but Arang is no wilting female. And at the end, she regains her mannerisms from the beginning. Cue ending too.
Hi

I totally agree with you. The dizzy to the point of being dumb and submissive type does get grating after a while. Looking at your list, it seems that you have already seen some of the best dramas with strong female leads and there are some great suggestions above. I would definitely second Empress Ki and Queen Seon Deok, both of which whilst not rom - coms are great and have multiple female characters who kick ass, some literally and some in other ways. 

Here are a few others that I could think of:

I Need Romance 
Discovery of Romance
Cunnning Single Lady
Dal Ja's Spring (She starts out dizzy but grows stronger + other strong female characters.)
Heart To Heart (Despite the female lead suffering from agoraphobia, I still consider her strong in other ways, if that makes any sense.)
Ho Goo's Love
What's up Fox
My unfortunate Boyfriend
Kimi Wa Petto 
Reply 1997
Ex- Boyfriend Club
The Producers
The Lover

All of these are  Rom - Com - ish with some having an element of Makjang added.

Enjoy, Luna.

Cubic - its a thai drama and the female lead has all the quality's your lookin for 
http://mydramalist.com/9938-cubic

It's Okay, That's Love has a rather strong female lead