'u' is the default Interact With Target (or whatever it is actually called) in LotRO. I have a crazy melee team I made just to see how it worked out, it consists of a Warden, 2x Captains, 2x Champions, and a Burglar.

I sent ‘u’ to all the slave’s screens as the first step in my DPS steps in ISBoxer, and I also set ‘u’ to broadcast to all the slaves. Hitting ‘u’ should also turn on auto attack if your target is hostile, so the character should run up to it and start auto attacking.

I forget if this works with skill forwarding, you might actually need to have the hostile targeted.