Instant kill ignores durability, it's not conventional firepower. Even then, given it drains lifeforce, it's sort of dubious as to killing largely superhuman opponents. Even then, it's so goddamn slow
Shields? How durable. EDIT: Why would they matter when telekinesis isn't something you can block with a barrier
Disarming spells. So?
Jedi and Sith just use telekinesis to get their lightsabers back. Oldest trick in the book. Hell, use TK to snap their wands (if Harry Potter can physically break it, yeah)
How durable? Still wondering why it means shit when, again, you can't stop telekinesis with barriers
Jedi and Sith can resist mind****, so good luck trying to possess them (unless Potter-verse possession works differently then mental possession)
Jedi and Sith can still mind**** them, invisible or no
Flight. Can still be TK'ed or force lightning'd
Not to mention Jedi and Sith are far faster, they'll be able to move first
EDIT: Hell, even lightsabers are far more energetic then Harry Potter wizards