Originally posted by: Chandraketu
Precisely!
Also, in the versions that do have Ravan battling Dasharath, the battle ends in a stalemate, and Ravan later asks Brahma to grant that no sons are born of Dasharath's loins - which is why he needed to perform that yagna. Also, those battles did not feature Kaikeyi, from what I remember seeing (only place where it's shown is the ZeeTV serial Ravan.)