TheWoWDBAs Horde, I found the following NPC worked:
Thane Stonehearth (he is walking around on the beach near the Alliance base.)
And the following NPC did not:
Fenix Hexwrench NOR his charge (Fenix is the bodyguard) nor his charge's succubus.
So, no, any random Alliance NPC with 800k health does not work for this quest. Go after Thane Stonehearth. It is also worth mentioning that the rares (Dalan, Mavis, and Disha) do not count, either.
Quest
Hero Killer
Quest facts and objectives from the current retail game data.
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
It is worth noting that the Mountain King is one of the Human heroes from Warcraft III. The others were the Paladin, the Archmage. The expansion set introduced the Blood Mage, but that was actually a blood elf.
The NPC that you're looking for is [npc=67636] .
He spawns at 81.16 , 23.46
At a glance
Hero Killer is a Horde-only quest for level 15-35. It rewards 1 reputation reward, 4,800 experience and money.
Quest facts
LevelLevel 15-35
CategoryLandfall
Quest ID32135
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(32135))
Requirements
RepeatsDaily
FactionHorde only
Read from the Blizzard quest API.
Description
There are some situations in which taking out one of their soldiers is more important than killing hundreds. They've deployed some of their heroes to the battlefield to help rally their defenders. Not only will killing them soften their defense, it will also leave their morale crippled. So go, take one down for me. You can handle it.
Community notes from Wowhead · 13 comments
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Reward details
Reputation: Dominance Offensive +300
Horde forces in Pandaria, stationed at Domination Point in Krasarang Wilds.
Reputation group: Mists of Pandaria.
Currency: Lesser Charm of Good Fortune x 2
Possession of the Lesser Charms of Good Fortune will result in great happiness and the eventual conversion into Warforged Seals, which allow players to risk a coin to receive a bonus reward from raid encounters.
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.
Where this quest fits
Other quests with this name
This one: Horde only · Level 15-35.
Steps, storylines and map placement from the client’s QuestLine, prerequisite and QuestPOI data; neighbouring quest text is Blizzard’s own (quest API), shortened to its opening sentences.