This was fixed ages ago, you should make sure you are updated, or if someone is broadcasting to RW, get them to update.
Quote from grubly »
The exact workaround should be
if unit == "player" and name == "Rampage" and remaining then duration = 30 end
to avoid the Lua error.
It is just a workaround, and you have to replace "Rampage" by the localized version of the technic, "Saccager" for example.
Without this little bug, this add-on would be perfect. Just perfect :)