I got my Glimmer with the weirdest combo - Splatter/Infinity about a year ago. Glimmer is going to be very hard to breed because it's so difficult to keep the Rainbow from splitting into blue/yellow. I would say keep trying. Eventually one of those dragons will fall into your lap.
For Chakra, I got him with Emerald/Infinity.
As for Black Diamond and Prime Eternal, those are my unicorns. I can't breed them for anything, lol.