I’m not a big elf player so I’ll bow to others’ experience here. Nonetheless I’ll elaborate on my thought process here.
I just don’t like how extreme it is for weapons like longbow and hagbane. Either you take Kurnous and are swimming in ammo, allowing a very ranged focused playstyle, or you don’t take Kurnous and the difference to your ammo pool is pretty stark. Certainly not unworkable for longbow, but you do give up a fair bit of ranged uptime if you’re not always hitting heads Yes you can go the Scrounger route with swift bow, but you give up potentially running barrage or Hunter which seems a significant loss compared to just letting Kurnous handle the ammo regen and benefiting from all the bonus damage.
I’d rather see Kurnous given a reasonable restriction, like proccing once per Ult, and giving her other ammo sustain options to spread that regen a little more thinly across more builds. I certainly don’t think her current ammo regen with Kurnous is too little compared to other ranged classes. Quite the opposite.
Anyway I’m no WS main, so if people who play her more think it’s fine as is, sure, I won’t argue further.