The Assassination Mode is a cycle.
Well, I think that at least. Each one having a target and after killing the first target you'll get his own target looks awesome to me.
Edit: I guess it was to good to be true... A friend of mine helped me finding some flaws.
Samurai: His Dash is not really good, since it does small damage and does not slow or stun. Make it have a mini stun of 0.5 and make its CD shorter. Perhaps increasing the speed and range of Wind Gust. Also, his tornado is OP. Basicly, a undodgeable and ranged attack. Instead, make him have a fast arrow with the same damage as Dash. However, no cast. Also, maybe rename Dash to Leap.
Ninja: Incredibly underpowered. Make its Shurikens have a longer range, and instead of Transmutation...
Make a skill in which he casts for 1 second, then blinks towards a position (and before blinking, make a fast invisible shockwave of 55 dmg). Resuming, the skill could be Blinding Speed: Ninja focus for a second, then slash everything in a line faster than the eye can see. Or add that to the empty spell slot Ninja have. If you actually plan on removing Transmutation but can't think on something else, then tell me.
Kunoichi is the most balanced one, but still could be improved. Make Swift Charge a bit faster, and instead of lockdown, make her throw a poisoned needle (which would be a mix of slow poison and that Warden poison skill... don't remember the name.) 50% movement speed reduced and 3 damage per second during 10 seconds. (Most military women were very skilled at throwing needles, so makes sense.) And for the empty slot, a buff that give you 50% more attack speed for 6 seconds.
Glaivemaster: I lied about the Kunoichi, he's (she's? The description says this hero is a woman, but the model looks like a man...) the most balanced. The perfect ultimate for him would be some kind of fan knives. If making a custom version of it (making actual projectiles instead of just a aoe explosion) of shurikens. I don't know how much damage per shuriken there could be...
Also, I saw a pretty much interesting program named the Mortal Weapons of the East. Showed some nice things. All of them could be used to make more heroes, although I couldn't imagine of skills using them. There was a exception, however.
Monk: First thing about the Monk. Since he's using a staff, you might say his weapon wouldn't do as much as damage as the other weapons. That's simple: Just make him do 30 damage with double attack speed. Also, he's a Chi user! Thinking again, you could give him normal 55 damage, even being just a staff, because of his Chi. He enhances his staff with it

About the skills... Heart Strike. Does 55 damage and stun the opponent for 1 second. Or, what would make it more heal, since the opponent's heart would be hit, would be to be 40/30 base damage and 3/5 slow poison damage during 5 seconds.. Description could be something about Chi. Then a skill with the area of a cone, with a great AoE, also doing 30 damage. Could be also called Chi Attack, extending the chi through the arms, through the staff, and a bit further, which explains the increased area. Then sometime of Wind Gust, but around all the Monk, with the speed and range of the current Samurai (And since the Samurai's wind gust, as I suggested, could be better, it would be balanced: area for speed and range.) For the fourth skill, I'll make the "teleportating" one. Using his Chi, the Monk levitates for 6 seconds, and is also a bit more faster. Or whatever else you think of. For the fifth skill...
I have absolutely no idea. You'll have to think that one out. For the ultimate, however, would be a bladespin with a cast time of one second with great AoE (thanks to Chi) and 20 damage during 3 seconds, also slowing everything caught by it.
Also, put animals on the map, for many reasons. First, if you keep the Transmutation, it will ACTUALLY allow the Ninja to mesh in the environment. And it will be more realistic. And make them respawn, since some creeps may actually die a lot with many AoE skills. Well, I don't know. Since you're "allied" to neutral pacific units such as animals, and your AoE skills don't target allies...
And don't forget about my ideas for more Arenas! (Not just one Castle Arena, but three urbanized arenas, one for each ammount of players, so that there are more options to choose... as I said before.)
And AGAIN, you might want to put some soundtrack on your map, but you don't want it to have lots of space. I've HEARD that a program named Imtoo Audio Decoder can shrink musics wonderfully and keep the same quality. Try it and see if it is truth. If it is, congratulations, SB will now have a soundtrack!
There it is. I hope that THIS time it will be flawless.
(I fear I may have made the Kunoichi OP, but if anything you'll just test with someone before releasing the official 0.70 version)