I have added two servers A & B in SharePoint Farm. I have dropped cross domain.xml (As I am accessing the WS services from browser) in Server A but not in server B. I am accessing the SharePoint webservices pointing to Server A. After setting-up, I have found that SharePoint ws calls are very unstable than when I interact with Sharepoint installed as stand alone. Does it mean that though I am making request to Server A, but it internally routed to both the servers. Does Alternative Access Mapping has any role to this. Appreciate your help.

SharePoint itself can not route requests inside Web Farm. You have to use for that hardware or software NLB. How did you find that requests routed on different WFEs? Oleg