Here’s a quickly assembled list. hope it helps some
1 (vanilla)
mini mindslayer, anubisath idol, viscidus globule - ahn’qiraj
giant bone spider, fungal abomination, stitched pup - naxxramas
harbinger of flame, corefire imp, ashstone core - molten core
untamed hatchling, chrominius, death talon whelpguard - blackwing lair
2 (burning crusade part 1)
lil bad wolf, menagerie custondian, netherspace abyssal, fiendish imp - kharazan
tideskipper, tainted waveling, coilfang stalker - serpentshrine cavern
pocket reaver, lesser voidcaller, phoenix hawk hatchling - tempest keep
3 (burning crusade part 2)
grotesque, stinkrot, hyjal wisp - hyjal summit
leviathan hatchling, abyssius, fragment of anger/suffering/desire, sister of temptation - black temple
sunblade micro-defender, chaos pup, wretched servant - sunwell plateau
4 (wrath of the lich king)
dreadmaw, nerubian swarmer - trial of the crusader
magma rageling, ironbound protowhelp, runeforged servitor, sanctum cub, winter rageling, snaplasher, go-r41-on ultratonk, creeping tentacle - ulduar
boneshard, blood boil, blightbreath, soulbroken whelpling, drudge ghoul, wicked soul - icecrown citadel
5 (cataclysm)
tinytron, discarded experiment, rattlejaw - blackwing descent
twilight clutch-sister, bound stream, faceless minion - bastion of twilight
drafty, zephyrian prince - throne of the four winds
blazehound, cinderweb recluse, surger, infernal pyreclaw - firelands
faceless mindlasher, corrupted blood, unstable tendril - dragon soul
6 (pandaria) - PTR, subject to change
stoneclaw, wayward spirit, comet, baoh-xi - mogu’shan vaults
korthik swarmling, amberglow stinger, spawn of garalong, living amber, ravenous prideling - heart of fear
azure windseeker, spirit of the spring - terrace of endless spring