Congratulations Sir, you’ve spotted my sarcasm 
Back to topic: Actually, we can use a key to cycle through friendly targets, so I think it’s reasonable to assume the necessary code for tab targeting still exists.
What about implementing an option to switch from friendly to hostile targets ? A bit like the option to allow/deny/ask for meet-up requests.
I just did a small test: using the reticle, friendly targets get highlighted when under ~10.6 meters, while the distance increases to ~25.4m when tabbing. Hostile target through the reticle are detected at ~27m (not 100%, the number is hard to read)
Also, during the “Message to Hell” side mission in KD; there are 3 crates you got to destroy. I used elemental skill to damage those, and it required 2 hits (thanks not to laugh at my dps output
). Thing is when the 2nd hit landed, my reticle was way off the target, like ~30° away. So, there could possibly already be some kind of “soft lock” but for static targets, OR I had my aim on the crate when I pressed the button, and moved the mouse away while the already queued ability fired, OR these crates got a rather large hitbox. More investigation will be done (if I don’t forget about it ^^ )
Sometimes, even with only 1 target that is not moving, in close range - less than 10 meters- just barely 1° off is enough for the reticle to lose aim. It feels like you can’t hit the broad side of a barn (I had to search for that expression - english is not my native language). To me, it’s like either the reticle algorithm is really not accurate, or the mob’s hitbox is awful (or maybe my hands are having uncontrollable tremors). Lucky for us, we’re not playing a FPS or a shmup 
Edit: the friendly target tabbing seems to be limited to a ~60° in the direction you’re facing (that’s an estimate)