The version one droids are pretty durable and even Draco might have a hard time dismembering them (but it's not impossible for him to do so). His size would probably make it easy for him to pin them down and keep them occupied. His fire breath wouldn't do much to harm them.

The Shift Hunters will be vicious and try and bite and claw at him, but it's possible his hide is thick enough they won't be able to harm him much. Although they're immune to fire, it wouldn't be difficult for Draco to rip them apart.