Theseus, if I understand correctly what a 'semi-filler' is, 'do y' hear?' can be ok in many cases, but it depends on context as usual. It literally means 'do you hear this?'. 'Are you listening to me?' can be ok, too.
Do you have an example?
"Τ' ακούς, τ' ακούς, μωρ' μαύρη γης το τι σου...