In its current state, the event isn't as grand as I hoped. You need 40 tokens for each item and there are only 5 items: a sienna goat, fiery yellow beetle, corrupted craban, cloak of shadows, hooded cloak of shadows. The cosmetic pets aren't really different from some pets that are already obtainable and the cloak doesn't appear to have any sort of special design/effect.
It appears that the deed for killing 60 harbringers is only counting at level 120 at the moment. Trying to kill one away from its initial spot via kiting tactics will negate the kill count. Killing a harbringer that spawns after the skirmish has "completed" does not count either. And in the dry run I had yesterday, you must kill one your current level (though there are ones that say going above your level as well).
A lot of people are saying that certain harbringers are actually impossible to defeat at level cap while ones at lower levels are actually quite easy to bring down. And the skirmish assault seems to complete when you do 3 out of the 4 listed.
Hopefully the developers will try to get their act in order because the event sounds like an ultimate fail in my eyes.