I got the Sea Shell Sleeves quest today and this is the mob they want me to kill. I am a level 25 druid. These mobs con purple +++ to me. The quest they sent me on is NOT level appropiate and these mobs are NOT level 23 - 24.
Well in typical hibernian fashion - i recieved a grey leather helm with no special properties off an assailer that conned blue to me. In midgard you get a yellow and maybe even orange drop off a yellow con mob, in hib - lol - you lucky to get a blue con item off a yellow mob. OY! Anyway, the helm was called Worn Dark Shadow Helm, like i said - leather, 30 AF, 89% qual, and the kicker : no special properties.
While hunting the Waylayer Hammer from the gurite waylayers, my blunt specced Warden accidently aggroed an assailer and got a nice suprise: Ring of Blunts (4 str, 3 emp, 1 blunt). So yes, they do give drops.
There is a flavor of Siabra assailers called gurite assailers in the woods south of the path next to Ceannai (the way to Innis.) You need to kill one for the Sea Shell Sleeves quest.