This never happened to me using slingers, they seem to be pretty effective, on the contrary.

About horse-archers, they're like archers but 10 times as effective.They don't need support as they can run away from melee, they can flank the enemy and thus bypass the shield defense and they're pretty decent at melee(not the lighter ones, but the bodyguards, but the lighter ones can chase down routing enemies)
It's not even funny using them against the AI, but it's pretty interesting to face some horse-archers without your own HA's.I personnaly like to kill them using siege engines, hiding in a forest and them ambushing them or sending some unit as bait, and encircling them.
I've read that Alexander the great used this tactic against them in the Battle of the Jaxartes(Read it at livius) and it worked.



About the cretans bows I hope some EB member with better history knowledge than me can solve this question. But I will search the forum a bit to see if it's already covered.No luck using google.