Leatherworking : impossible to find the "tough scorpid" patterns

Hello,

my hunter (Horde Troll) needs to craft 2x (tough scorpid breastplate] & 2x [tough scorpid gloves] to get the Master Leatherworking in Bad lands teach me the Dragon Scale speciality.
But, after killing hundreds of Wastewander Bandits, thieves etc. in Tanaris, and spending many hours of game for that purpose , i never looted these needed Leatherworking pattern.
I am puzzled and would be glad to know if the related Leatherworking quest changed/or/became obsolete compared to what i lived when i played on the official servers.
A good information leading to the completion of that quest would be so much appreciated.

Thanks in advance :-)