Totally, if I had more time the drones would probably have dropped hearts sometimes.
Regarding damaging the drones, the game checks if you're above the enemy and falling when the hitboxes overlap. So you can't jump into enemies, only drop onto them. Try to line up the drop shadows since it might be difficult to judge the correct height, and hold the jump button when you connect to bounce higher. The enemies need to be closer to damage you, than you need to be to damage them.
Thanks for playing, and providing feedback! :)