The issue with murder bot swarms is machine vision is still expensive, slow, and energy hungry to put in a small enough package. Marking gps coordinates for a simultaneous drone bombing on the other hand...
We are a long, long way off from people-seeking HK drones.
You need several magnitudes of energy storage density (and/or electrical component efficiency) before you'd have a hunter-killer drone not just slowly moving over the battlefield grav-dropping a nade on a target. And that's to say nothing of the on-board computing requirements for autonomous operations.
The Switchblade is pretty big, expensive and, when climb/loiter is fairly loud, and is about the minimum size you can use to hunt for vehicles without human interaction. A tank is big, loud, and unnatural looking. A human - especially one that wants to hide - is much, much harder.
Most of the (semi) autonomous drones in use now require live-targeting be set by an external higher IQ (humans now, could be heavy-AI) and use very primitive image processing to track their targets. This works for tanks because they are not very manuverable. You can give an AI a tank shape and point it in the general direction. Even if you do something like dynamic cammo where the image of the tank changes and the AI gets confused, for as short flight time is as long as the drone is pointed in the general area and has the target's speed, its going to get the general area. That tank isn't going to suddenly be going 90 degrees to the side. Addition to that, the untold secret of a lot of these drones is they don't use just vision but also sound. Even as quiet as the Abrams is, that's a relative scale, tanks are very loud.
The racing drones are powered by ultra-high capacity capacitors - ultra caps - which give a ton of power but have very short runtimes and near zero storage potential (but very fast charge). And while they do crazy shit, hitting a target that can move like a jet or a helicopter is really hard. Modern SAMs & madpads just make it look easy - and pack enough explosives that "close enough" is close enough.