I am alliance and currently doing Scarlet Monastery ... really happy I decided to do the lock instead of a 3rd mage (the team is pally tank, 2 x mages, 1 lock, priest healer).

SM is quite the ride for alliance, so the fact that I can summon everyone, including the lock, is really helpful since I can hearth out for repairs, selling junk, buy the next level spells and so on. lol I just realized as I am typing this that I could run to the summon stone, but whatever, faster with lock summon :-)

That in addition to off-tanking, although I prefer blood pact, soulstone and healthstone.