I wish you are having a nice day, because I'm having one myself ^_^
And back to the bug my friends and I found, is like this:
Some rare/champs are listed in some Achievements, such as
- We are the Champions! （HC champ mobs collect)
-Trophy Hunting (HC rare mobs collect)
-Champions' Collection (SC champ mobs collect)
-A Rare Phenomenon （SC rare mobs collect）
But they don't actually spawn.
Each is listed below:
1, Sand Dweller (Neither of Rare/Champ) Have the look much like sand giants, and often appear on Desolate Sands, but my friends and I never seen a rare/champ ever, no where.
2, Dust Imp (Neither of Rare/Champ) Little imps spawn from structure in Kulle's Archive
3,4 Skeletal Sentry/Skeletal Raider(Neither of Rare/Champ) Both skeleton weilding a shield, appear in Act 2
5, Mallet Lord (Neither of Rare/Champ) I don't know if I should be thankful as I never encounter one of these rare/champ... That should be really though if I met one on inferno xD
6, Armaddon (Neither of Rare/Champ) Mounts of Subjugators
7, Subjugator(?) Champs spawn normally, but Acheivement won't be lit when I kill them. A bug, I'm more then certain.
8, Armored Destroyer (Champs) I met rare Destroyers, but no champs...
9, Horned Charger (HC only, champs) Strange enough, I think I've killed dozens of rares, but no champs
10, Harvester (HC only ,rare) Same as above, maybe I'm ... I've been having bad luck
11, 12 Rockworm / Savage Rockworm (HC only, Neither of Rare/Champ) I'm sure you guys are joking while add those things into HC achievement lists. No? Well. please fix it anyway, and I'd plead remove those from the list , not adding to the game! Seriously!
12.5, Disentombed Hulk (HC only ,rare) I've killed more champs than I bother to count, but no rares...
That's all of them, may be there is less that is bugged, and I'm having really bad luck...
And anyway, I'm having much fun searching those rares, and looking forward to meet more of them =]