Disable is definitely a must-have. The undead ghast-fiends (the ones that can teleport) are weak against disable, and I’m 95% sure the skeletons are, too. Just cast it on everything, then attack. (Except the bombs..they’re neutral, leave them alone.)
(Be careful, at the end of Barheim, there is an Esper…don’t go past the very very last save point.)
Alternatively, you’re probably at a decent level to go to Golmore Jungle. Once you get "Lente’s Tear" you can find a sweet skeleton spawning ground in the Southern region of Golmore.