Tin doesn't add that much protection. It's great for passive interference, but for an active high energy system, the best it could do was heat up instead of the elctronics. But it'd have to be anchored to the drone somehow - and those anchor points, or the tin itself, would need to be able to effectively shed a couple hundred degrees of heat pretty quick as more energy is pumped into the system.

You could negate it with a faraday cage, but then it couldn't communicate back to base, be remote controlled, or scan things via em or visually after launch....it'd basically be a dumb missile or rpg at that point and not a drone.