temptation did drop from hk in a f e hm before 1.3. i have yet to see hk drop this weapon afterwards. either it is a very rare drop now after his loot table was upgraded or it was removed.
I had Temptation drop off HK-47 24 hours ago. So TEMPTATION has been confirmed to drop from HK-47 as of patch 1.5. Hopefully they won't touch his loot table.