Honestly, I think Vic Mignona is quite an appropriate voice actor for Keldeo! He sounds confident, headstrong, determined, and a little brash! I imagine some people will here his voice again and compare Keldeo's character to Edward Elric's and notice some interesting similarities!
They gave Virizion a rather girly voice, by the way, which kiiinda makes sense because he's based off of the more feminine-leaning man in the Musketeer Trio, but yeesh, kids are gonna think Virizion is a girl for sure!