Cabal are extremely coordinated, and from the looks of it, are winning over Mars. Their enemies? The vex. Apparently the vex can't beat them. What I see happening (if guardians didn't get in the way) is the cabal winning over Mars, the vex time travel a pocket of its military, rebuilding, and then going back to fight the cabal again. I see the vex as a never ending supply of enemies, but not necessarily the strongest. Upon pushing the vex back, and exterminating their time gates, the cabal could definitely take Mars.