With the exception of Cristina Vee (Killua) I don't really recognise anyone.
I can't really picture Vee doing a good Killua, Granted I only really know her as Mio and Compa.
Leorio getting replaced is kinda sad, The '99 dub really nailed him.
I read the manga first and his dubbed voice was pretty much spot-on to how he sounded in my head.
Here's a peek.
Erica Mendez (Gon) voiced Ryuuko in Kill la Kill and will voice Sailor Uranus in Sailor Moon. As for voicing little boys, she voiced Aladdin in Magi.
Matt Mercer (Leorio) does Levi, Chrom, Jotaro, Law. You get the picture.
As for Keith Silverstein (Hisoka), he voiced Johann Liebert. So, I'm sorta optimistic for that.