The reason this mob is called "Galkarider" is because he is a BST and can (and does >.<) use charmga. He's irritating as hell to kill and I try not to engage him personally if at all possible. If you can, get your BLMs and RNGs to nuke/shoot the crap out of him.
Galkas aren't the only ones being picked on as you can see by these other little gems found in Dynamis-Beaucedine: Elvaanlopper Grokdok Humegutter Adzjbadj Mithraslaver Debhabob Taruroaster Biggsjig