Countering End-Game Astral

[Agema]

Smashing the whole battlefield with big damage spells on the first turn or two before big buffs tend to arrive is a recommended tactic.

Also, master enslave is easy resist as I recall (+4). Add in Army of Lead (Earth) and ?Antimagic (Astral) each at +4MR and you should effectively be resisting at +12. Even if your opponent adds in some penetration, you'll lose only a very small chunk of your army. A bigger problem may be your battle mages targeting enslaved troops and catching your own troops rather than the opponent's big concentrations of units.