can I be sued without seeing evidence? What are the risks in

If you've asked for debt validation, they cannot sue you unless and until they've provided you with that validation. Unfortunately, if half the stuff I've heard about allied interstate is true, it doesn't sound like they're particularly concerned with obeying the law. :-(

On the up side, if Allied does sue you without any documentation, they're basically just shooting themselves in the foot. Under such circumstances, you can, and should, countersue for violation of the fdcpa. Also, I'm not quite sure what you mean by them "reporting your debt while it was being disputed", but depending on what, exactly, they "reported", that may also be a legally-actionable FDCPA violation.

Standard disclaimer: I am not a lawyer, yadda yadda.