I'm 40+ in all 6 crafts and do all 6 writs every day, my best day in the last week was 3 gold materials, some purple provisioning materials and 2 surveys. My worst has been one gold material.
I think what you are seeing is the RNG at work, but I would agree that the equipment writs investment/reward is borderline not worth doing on average. I only do them because over the 6 writs each day I rarely end up in deficit, but some times the RNG hates me too!
Perhaps they were, the last one I did granted me an Almandine. That's it. One Almandine.
Most of my writs and hireling mails are like this lately. No surveys, psyjic or glass fragments. No purple and gold upgrade mats. It's becoming a joke for the amount of mats, skill points and time. Not to mention the aggravating freezing and crashing in wrothgar trying to turn them in. I think they nerfed it right into the ground.
Ive noticed the rewards have gotten worse. I used to get around 6k gold and 10k xp but recently Ive only gotten about 4k gold and 6k xp for doing all the writs. I have a character that I use solely for crafting and he is lv 50 in all crafting abilities. I have done them daily for several months now and noticed a big drop off in surveys over the last week. I used to get one to two daily now I'm lucky if I get one every other day.