Ok let me do this properly this is edited to to what it should of been before I accidently deleted it on my phone >w>
First lemme state the female concept, You're right if it was a champion then that's fine with clothing being the same it's just... a bit too much though or at least too many things, I like a white kimono with red sash's, idk why I just do, and then you have her with long braided hair cool you have a feather okay that's neat, now she has pink ankle sashes, w-wait what? why, we can't see them. The Navy blue fingerless gloves don't really shine that much to me though and they seem confusing on her with a kimono. The knee boots are very odd to add in when she's wearing a Kimono that covers her boots pink ankle sashes. The way I do see it working though with the added things is a hunting tunic underneath and leather pants making her agile with something comfortable under neath the kimono. I love though, love, the weapon choice you made. Daggers fit this character well and it gives range to different types of what she can be, heck you can even through a katana on her and have her be a bruiser assassin something like Fiora but Ionian style, no I don't count Yi at all.... he's Yi.
If she's a summoner though change the appearance every so often like clothing make her a normal person that changes clothes. That's about it.
ok back to the Champion OC, have his armor out and him flaunting it, have him flaunt his looks flashy attacks, flashy movement he wants attention..... make him like Draven, that's due to the taunt at least and how you want him portrayed.
Your Q is fine really a 1 second melee stun which you can buff to 1.5 like most stuns depending on the ad ratio you want for it though, if it's high keep at 1 if low bump it to 1.5. Now for the c/d it needs to be amped up to say 7-8 seconds cool down and it's fine then. Just look to Leona's Q has a 11/10/9/8/7 cool down on it.
The W needs to worked out. First I say change to the range of Kassadins slow because the range on it is too strong for it. The Cool down needs to be increased as well to about 15 seconds or reduce the sight, which it does anyway to maybe about 2-3 seconds since it's an aoe champion revealer. The slow on it can also be reduced to about 20% at all levels due to what it already does adding a slow is making really strong on its own especially since it's not like Ashes volley in a sense it can be blocked that's my tid bit at least.
The E is actually fine, it's well and does fine, just have a somewhat low ratio for it and a longer cooldown like 7-8 seconds because Ez's it has a 11 second rank 5 cooldown but it's also due to his Q ability passive so ye just the cooldown for now.
The Ultimate brings a **** ton to the table of utility. It's the broken ability on this champion. First the length of it, I'm going to say reduce it right away to 10 seconds due to what it does exactly and maybe have the crit chance come out to be 15/20/25% crit chance increase. Keep the add on abilities, have a low ad steroid compared to others at least and there you go, make these changes and it'll be fine.
RQ. This is too much for a single ability, you have strong 2 second stun plus a straight line knock aside. I would say increase the AD ratio on it but keep the stun the way it is 1-1.5 seconds. Take out the fissure though and maybe replace with either a cleave or a 100% chance of critting a stunned or suppressed target for a passive when the ult is activated of course.
RW. Humm eh. This is where you can pump it up to a 35% slow ratio, increase the range to Ashe's Volley or less maybe a bit of an increase in range but not width, and reveal champions for 5 seconds now it still brings A LOT to the table but it's still reasonable to a sense so this is the change I say making to it.
RE. Just have the damage increased that's it really, the range is not needed with the cool down it already has otherwise you ahve a Kass ult with no draw back essentially.
Anyway that's my tid bit, I have done a champion concept before as well and I did it poorly I tried to make the changes to make the champion balanced but I couldn't till I finally looked back on the champion and read out loud what she did. So I know what this is like of making a champion at least and learning from the mistakes that I made, and I made a lot. So if you find this post mean just tell me and i'll keep my word in removing this post.
also here's the site that I pulled the cooldowns, ratios, and what not from http://leagueoflegends.wikia.com/wik...f_Legends_Wiki