Here's one that I use,

/enemysign attack1 <t>
/ac "Target Forward"
/wait 1
/enemysign attack2 <t>

the targeting back and forward can be used like a action macro like all the abilities listed in Power & Traits

But beware of adding more than 2 signs automatically as the Target Forward will rotate back to 1st enemy in list if there are not enough enemies in sight, thus marking it with another sign.

I will post in Tank macro thread for the macros I used to target enemies marked from 1-5 in sequence and also the macro for re-assigning 2-5 signs in sequence to attack1.

Hope it helps