Got my drop in less than an hour, just clearing the tunnels to Qinimi and Riwi and any Screambringers that happened to pop in the central area. Got my drop in the tunnels leading to Qinimi.
Just got my Jaw for Pal 1.5. Had heard some say all drops can be done in a few hours, but this one did not for me.
No less than 4 trips to Barindu, minimum 1.5 hrs per grind. Hit Ferubi zl, Qinimi zl and Vxed tunnel ent. Finally dropped near Vxed tunnel.
Theoretically, there are more spawns of Screambringers near Qinimi tunnel/zl, however there are no named there, and the Vxed cleric 1.5 spawn NPC is near Vxed also.
Another friend of mine also got his at Vxed tunnel while doing the cleric 1.5 event. Makes it easier to find MH to do both at once :)