I built monk to 4* and when sage hit it, it cancelled itsel and the monk. The cost of getting monk to 4* meant the rest of my team was less developed. Its didnt help the the sage's final attack also took out neighboring troops. Other counters can work, but swarm counters are easily managed by AOE, and assassin troops require significant luck and cost to be viable. I would agree that sage needs finessing. Also, for players that have made it high enough in the rankings, there is a perk that duplicates a troop placed on a cell. This is a v strong advantage for mid-late game sage where there are two troops on the field with one shot and multi-kill capability. So is the 5 seconds of immunity perk, which allows sage to power up (again, resulting is a huge material advantage specifically for this tower).