I've never heard Cortana in any W10TP build (I'm an evil foreigner though).
Tick the field for English speakers with accents.
I haven't had any problems with Cortana on the last 3 builds(neither upgrade or clean install). Also, seeing that she uses Bing, I do NOT clean my history on Bing, only the cookies, from sites that are not my favorites or have to do with software I use. I think she even picks up stuff when I use Windows 8(I mean fills her data bank(Stalks me?) with what I search for, because she is getting better finding things when I ask on the net, more hits & a lot less misses.