Graspings are pretty easy to kill, the only problem is : They start running away fast. When you duo UW with famine/sb, the Ranger must be far enough away so the graps dont start attacking him. But still, graps are no big deal in uw.
Yes they loose aggro very easy.. but are, as stated, very easy to kill.. Just dont bunch them up with some other monsters, like Atxes.. Then the squids will go away to heal up, and attack the ranger..