Rasaad's Quest

What is the latest time to get Rasaad in the group and start his quest?

I have Neera and Dorn in my group and I want to keep them. But I dont want to miss Rasaads quest. So I'd like to get him in my group and just do his quest with him and afterwards I want to have my old pary back.

So is there a latest point I can have him in my group?

And a second question: What would be the earliest time to do his quest without getting killed all the time??

Thanks for your answers!!