Excellent thread my friend.
The key here is obviously teamwork for the ninja. That shouldn't be much of a problem. I see the best strategy for the ninja as this.
Kasumi will act as infantry. Due to having the quickest teleports and quickest charging ninpo, she'll be able to hang on the inside the longest. Her goal isn't to destroy them herself. Her purpose is to halt their progress and hopefully trim down their numbers a little.
Hayabusa will also be infantry, but his job will differ slightly. He will engage up close but will use his more powerful ninpo to keep the Tarkatan's close together. He will probably hang around the edges of the enemy a little more.
Hayate will go in and die......jk. He will comb the outskirts assisting Hayabusa when he can. Using his Torn Sky Blast, his primary purpose will be guarding the ace in the hole which brings me to......
Ayane. She will surve as the group's "tactical nuke". While Kasumi and Hayabusa handle crowd control, she will charge her ninpo. Hayate will handle any stray uglies that come her way. When she is ready to blast, the other three teleport a safe distance away.
Now, Ayane's blast may not kill every warrior there. If that happens, all the ninja will rush in to slay any stragglers.
It's a LOT of people to fight, but I think they can do it.
However, Hayate will die in the proccess.