Seems to me, that Shield Drone saves are only a 4++, but some of the characters and the riptide have a 2+ armour save, and the riptide can even get to a pretty beefy 3++. So, there is a better save being attempted before passing wounds onto the drones, which means a less chance that drones are dying, which is pretty neat. But, any drone can do this, so there is that.
For shield drones, they are quick and fairly tough. a 4++ and T4, so they can probably tie up marines and equivalent units in combat pretty well. They can be a great spoiler unit. Rush them up, charge folks trouble units, so they are stuck fighting drones or retreating and doing nothing. They are fast enough to sneak in your opponents backfield pretty quickly too, so could threaten any sort of heavy weapon squad or vehicle as well, taking their shooting away for a turn.
For scary assault units, toss in the drones (who'll probably not all die), burn 2 command points to keep them from running, and then if they survive into your next turn, just hop out of combat again.