so ive been playin crpg for 2 years now: gen 16 lvl 35, never once have I killed someone with a keyboard and mouse. controller is certainly effective for crpg, I think some things are even better with it than a mouse. the key is your right stick sensitivity, you want that basically at max so you can turn real easy.
i think especially new players would like the feel of mount and blade with a controller, it always felt natural to me.