what I would add to increase the HC population is simple " add HC specific Content"
lvl 1 Quest “Introduction to HC” a NPC wearing some kind of iron gear of appropriate faction race
a) kill 5 boars/night sabers, sign the “Hardcore Death Waiver” get 300xp to complete the quest
lvl 10 " Knowing the Ropes" Hardcore specific Quest
a) Discover the HC Death Statue listing all the latest names who died in that day (max 25) reset every 24 hrs server time , acknowledge the deaths click the statue so either a cry/salute get 600 xp. Statues are located in orgrimmar/stormwind
lvl 25 " Explore the Depths" Kill a specific Hardcore Boss in BFD rewards a Staff/Bow/2H Axe/ 1H Sword
Stats are 15+ Str, 5+ Stam 5+ Spirit 26 DPS 45-99 Damage ( 2H axe) and 1H Sword (8+ str, 3+ stam 3+ spirit)
Staff and Bow are 10+ Int 10+ Agi each
lvl 40 " Forgotten past" explore STV and kill a elite Hardcore Boss for a Ring “Blood Forgotten Band”
Stats are 10+ Str 10+ Int 10+ agi 10+ Stamina 5+ spirit equip: increase hit by 1%
HC needs content to bring players these are just some free-range suggestions I made for HC specific Quest