For mass killing the Rorarii at the entrance are best. Bring full armadyl/pernix, dual CCBs, ppots and ext range/ovls. If you have a superior ranged crit scrimshaw already, you could bring that too. Pray soulsplit and anguish, camp until bored/out of pots.
Alternatively you could try buying keystones and killing legios, though you would have to get the signets for an ascension cbow to pay for the keys. Gear would be the same, but you should bring 3-5 pieces of emergency food. Tactics would be running in a circle a few squares away from the legio, stopping to use an ability every 3-4 game ticks.
As Ping said, Sirenic scales haven't been added to drop tables yet, so killing them before that update goes live would not get you any scales, though you would still get xp. After the update, finding a free world will be hard.