When I first purchased the Diamond Temple (back when it was first released) it did absolutely nothing for me. I didn't get any Diamond type dragon while it was active and felt it was worthless.
I reactivated it for 300 gold just 2 months ago because I had several people tell me it was working great for them. With lots of speed breeding (600-700 gold worth) I ended up with 2 Crusaders, 3 Quetzals, 1 Anubis, 1 Angel, 1 Unicorn, 1 Helios. I was very happy with the results because around 1000 gold total for all those Ultra Rare dragon really is good IMO. Since then I have told people it's a good buy but only if you have plently of gold to speed breed, if not don't buy it.
With the temple on sale for only 100 gold I couldn't help but reactive, since I'm trying for Prism. I have now spent about 400-500 speeding and I have got..... wait for it..... nothing.
Now Teamlava is a company out for your money, there is no doubt about that. If they were not they wouldn't be able to have this game that we all love and sometimes love to hate. lol Yet, now I'm wondering with the temple on sale if they have tweaked it and made it not work as well even with speeding. If that is the case I think it's totally wrong but at the end of the day there is nothing that can be done except to never, ever reactivate it again (and never recommend it to anyone either).