The problem is ,a bad accent makes everyone laugh except the one whose accent is concerned...And as I'm a French speaker, yeah, I don't like at all how Ana is speaking while Hayato doesn't bother me as much. Of course it's bad,but in a way, it's funny because that's how many people in the Western world pictures a Japanese guy's accent.
As for personnality... I don't agree with the fact that it's hard to create a personnality for a killing machine. Foster, Alberts ,Masterson ,Briar, Scully and Hayato certainly have something that makes them likeable , either the insanity of Hayato , the oh-so british insults of Briar and Masterson to the funny quotes of Foster,Alberts and Scully.
Ana and Donovan on the other hand... They come as bland. But at least Ana has the benefit of having an original look and being the only female as of now. Donovan has nothing...