Mine Supervisor's main strength is generating lots of Bloontonium in combination with Bloontonium Miners and other Mine Supervisors. It is an important Monkey for Heroes that depend on Bloontonium, such as Adora and Mountain Obyn.
With 3 copies of both Bloontonium Miner and Mine Supervisor, getting their Bloontonium production going in the early game is fairly consistent since the odds of not getting at least one of them in the opening hand after 3 mulligans is very low.
The optimal combination of miners (3 Mine Supervisors plus 2 Bloontonium Miners) gives 17 Bloontonium at the start of each round. This is enough to generate full Bloontonium or close to full (for Gwendolin, Mountain Obyn, Amelia, and Striker Jones) in a single turn.
The lone Mine Supervisor is simply a more expensive Bloontonium Miner with much better damage, but no immediate Bloontonium gain. As a Rare, it is also a candidate for Rare Power.
This card has the same cost as Crossbow Monkey but 10 less ATK. While this card has less burst damage, the Bloontonium generation gives it much more utility, and can consistently attack Bloons each round.
While its damage per turn is decent, it still struggles against Aggro decks without additional assistance.