I think currently mangos works a bit incorrectly with trigger spells, I can't check it at bliz, but I hope devs will handle this.
Current mangos state:
for example
1. Shaman casts Earth Shield at friendly player, for example Warrior.
2. combat log says: [original caster - Shaman's] shield heals [caster - Warrior] blah blah.
I mean that doesn't matter who cast trigger spell, mangos will recognize original caster (who applied aura) as caster.
Maybe it is bliz like, I don't know.
So what is the problem?
1. Boss Akil'Zon at Zul'Aman cast spell http://www.wowhead.com/?spell=43648 at enemy target
2. 43648 triggers http://www.wowhead.com/?spell=43658
3. 43658 triggers http://www.wowhead.com/?spell=43657 that has TARGET_ALL_FRIENDLY_UNITS_AROUND_CASTER
5. mangos casts 43657 at all Akil'Zon's (original caster) friendly units, that is wrong