Vayne with Rageblade
Vayne's W stacks two times an auto-attack while Guinsoo's Rage is active. I think this is bug cause never seen it before.
Ex: 2 AAs proc the W true damage

Vayne's W stacks two times an auto-attack while Guinsoo's Rage is active. I think this is bug cause never seen it before.
Ex: 2 AAs proc the W true damage

Read what Guinsoo's Rages does.
UNIQUE – GUINSOO'S RAGE: Every other basic attack will trigger on-hit effects an additional time.
This is not a bug.
Nope, it's always worked that way. Same for Jax, Yi, Aatrox, etc