Remember this is just a trial thing and they didn't want to spend a lot of money on it right off the bat. It would be stupid for them to spend a gazillion dollars to license something like One Piece only to have nobody watch it.
If enough people watch they can start adding more/better shows in the future and give it a better time slot. For now, having it sandwiched in with the existing AS anime block means that the regular Saturday anime viewers will already be watching which is a sensible strategy imo, since they're the ones who have been clamoring for more Toonami.
I think the shows they added sound pretty cool though, esp. Casshern.
To me, nothing beats the classic line-up. I'm not all into the new animes nowadays. Cartoon Network has turned from a fun awesome channel for kids to a what the heck animations and the Adult Swim line-up is a bunch of ugly drawings that I get sick of seein and they aren't humorous at all.