Not sure if I was lucky with timing or if something changed in the today's mini-patch but I logged in during a sandstorm and there were silithid hatchlings all over the Gaping Chasm and Noxious Lair. The hatchlings were also quickly respawning after people battled them. This behavior is quite different from what I've experienced over the my last week of trying to get one. Previously I would login during sandstorms and would not see a single spawn over 45+ minutes.
If you still need one and were taking a break from trying, you may want to try again.