The idea with the Kroot wasn't to actually kill them in melee - especially with the Cents having ATSKNF and a 2+ save, it's a lost cause. (And FNP, if they're Iron Hands!) The idea was more to tie them up and allow the rest of your forces to worry about something else. The Kroot will die, and will probably need an Ethereal to keep them in combat, though. Maybe even Aun'Va, to put up both Stubborn and FNP to maximize the tarpit.
As far as point cost - Draigo is major-league expensive and a Lord of War now, but he's not essential to making this work. The version I played against was 3 Cents, Tigurius and a Librarian that started out there but moved over to a unit of Terminators later. The basic version costs about two well-kitted Riptides; that's a lot but in a 1500+ point game, there's still a lot of army left. You could do it without Tigurius, too, with just a basic ML1 Space Marine Libby, if the dice like you.
Watch out, also, for the Eldar version of this that uses Wraithguard with a Spiritseer and/or Farseer, too. Weaker saves, but meaner guns and majority T6.