[Phanx]

I don't know of any dedicated addons for that purpose, but you could use any of the numerous tooltip addons that show you which group members are targeting the unit (eg. mouse over a unit nobody should be hitting, and see who is targeting it), or a combat meter addon showing damage taken by NPCs.

Or, here is a macro that will tell you which raid members are targeting a unit they can attack that is not the same as your target:

/run local g, n, t, u = UnitGUID, UnitName, "target"; for i = 1, GetNumRaidMembers() do u = "raid"..i; if g(u..t) ~= g(t) and UnitCanAttack(u, u..t) then print(n(u), "is targeting", n(u..t)) end end

If you want to use it in parties, change GetNumRaidMembers to GetNumPartyMembers and "raid" to "party".

MoP version:

/run local g, n, t, b, u = UnitGUID, UnitName, "target", IsInRaid() and "raid" or "party"; for i = 1, GetNumGroupMembers() do u = b..i; if g(u..t) ~= g(t) and UnitCanAttack(u, u..t) then print(n(u), "is targeting", n(u..t)) end end

You'll get false positives if you have an offtank holding another mob, or something, but it shouldn't report healers since it checks to make sure that the target is attackable before reporting.