Why are wyvern gems so hard to get?

[Bastila Shan]

It’s so annoying I’ve been farming missions that have it as a reward and it’s not dropping after hours of trying

[Gaidax]

Just wait until guaranteed wyvern gem monster spawns and do that.

It happens frequently.

[Eventide]

You could also look for investigation SOS with wyvern gems as a reward. That's what I do when I need them