I'm quite surprise that apparently nobody has this problem.
In Italy nobody can use with satisfaction Whatsapp, because it crashes with Voiceover.
It crashes when a new vocal message arrive, it crash if you are scrolling recent chats, and sometime also during new vocal message sending.
Now, I can ensure you that using Whatsapp on Ios8.02 and ios8.1beta2 is absolutely tricky.
If I switch off Voiceover, then Whatsapp become a normal app.
Have you this problem?