I try to get this shield and Aspir Knife last nite. I work it out with lv17 RDM/WAR (me) and a lv19 BLM/WHM. Zxuu Buxu the Silent is pretty easy to us since we have Shell, Protect and Barstone. We manage to kill the mob and other 2 worms twice and each of us got the shield (statistically, 100%).
Spwan tile is about 15min (real time).
P.S. No THF is required.