Rek'Sai is supposed to be a Diver, so why

Why does she scale so horribly with AD? And why is her only engage tool, her ult, an execute meant to be used only at the end of a fight?

Divers are meant to engage and start fights with heavy damage and moderate disruption, contrasted with Vanguards that have high disruption but relatively low damage.

So why does Rek'Sai get neither? Instead she's relegated to the role of power farmer and mobile Control Ward with her W. The character doesn't even have a passive, or if she does, every other character in the game has additional passives that say "This character's W works as intended."

Prey Seeker (Burrowed Q): 60 / 90 / 120 / 150 / 180 (+ 50% bonus AD) (+ 70% AP)

Unburrow: 55 / 70 / 85 / 100 / 115 (+ 80% bonus AD)

Furious Bite (E) 55 / 65 / 75 / 85 / 95 (+ 85% bonus AD) (All damage doubled and converted to true damage at 100 fury)

Void Rush (R) 100 / 250 / 400 (+ 200% bonus AD) (+ 20 / 25 / 30% of target's missing health)

Her R is the only thing which scales well, meanwhile , a tank, get's 90% AD scaling on her Q (doubled to 180% on both hits) and the same 50% (doubled to 100% on wall slam) on her E, and a typical diver like gets around 120% bonus AD scalings on their abilities and often have % total AD to boot. I mean shit, Rek'sai's abilities do less damage than her autos when building the stat she's supposed to build, with the only real scaling coming from Q being an auto reset.

I get it, Rek'Sai is a broken character in competitive play because of the vision control she grants a team, especially in an organized setting, but why is that the only thing she's allowed to be?