The best replacement for warlock is hunter.

The best alternatives to warlock are rated as following:
★★★★★  hunter
★★★★★  mage
★★★★  rogue
★★★  priest
★★★  shadow priest
★★  shaman
★★  warrior
★★  druid
★  mage 5.4
★  paladin
★  wizard
★  hunter 5.4
★  mage wow
★  monk
  rogue 5.4
  warrior 5.4
  death knight
  mage pvp
  mage cataclysm
  shaman 5.4
  dk
  mage hearthstone
  sorcerer
  witch
  mage dps
  rogue pvp
  human warlock
  warbeast
  rouge
  warlock
  elemental summoner

Your alternative for warlock is not listed? Suggest!
Speaking about warlock, one probably shouldn't forget about green fire.

Other search terms related to warlock and their ratings are:
★★★★★ green fire
You have in mind a companion for warlock and it is not yet here? Propose!



Google Trends

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warlock
hunter
mage