Exile isn't meant to be played on Conquest mode. its set up so that pushing into the Citadel area is nearly impossible.
its a great map to play on Dominate, Fortress, or Slaughter mode though, try it out sometime. I know everyone plays Conquest by default but the other modes are fun too.
some maps are made for Conquest. these maps all have one thing in common: multiple approaches into the Citadel area and portals in the mid-map region that can be captured. the maps that are setup like this are Brothers, Mandala, Leviathan, and Cataract.
other maps have really interesting mid-fields but heavily shielded, choke point controlled Citadel areas. Crucible and Exile are both like this. terrible for Conquest really good for the other modes.
Prison is the one map that doesn't work well for anything except Slaughter mode. its super tiny and is basically a dueling arena. its also the only map you can have a decent 1v1 game on.