First character that comes to mind when i think mid-tier at DC is Hawkman. Both Hawks actually Hawkgirl, Hawkwoman. They have the weaponry to harm high tiers but they can’t physically contend, on a purely physical level with high tiers. Yet would soundly beat Street characters.
Mid-Nighter id argue is mustier, same with Beast Boy, New52 Lobo, Bunker, Aqualad, Wonder Girl, off the top of my head atleast