Apparently also drops from the grade 6 RNG box for 1000 wz comms.
The RNG box can either give you a Battlemaster (+31 expertise) schem or a War Hero schem (+41 expertise), but pretty rare, more likely to get random grade 6 mats. I bought 1 box on my artifice toon, got a stack of grade 6 biochem mats (red goo).
There has been no proof that this schematic still drops from those boxes.
As far as I know, the schematic no longer drops and some people are paying huge amounts of credits to get crystals transferred from other servers where someone did have the schematic from the olden days.
I made a thread on this issue, I doubt it will get dev attention, though: http://www.swtor.com/community/showthread.php?t=659523
If you are on The Ebon Hawk, someone will be transferring a shipment of them over from Prophecy of the Five: http://www.swtor.com/community/showthread.php?t=664197
Until something changes, Blue War Hero crystals will remain the rarest in the game, at least depending on what server you're on.