"Renekton's W procs on-hit effects"

Renekton's W does 3 procs at once. To prevent Shyvana from one shotting entire teams with her dragon's Q, there's a .001ish CD on Hydra to prevent multiple procs off of one AA. WW does 5 attacks over 2s, so of course each of his hits will proc the Hydra's AoE, though in all honesty, it's not really a problem given it doesn't affect his 1v1 and doesn't make his team fighting ability broken, similarly to WW and Shyvana.

Ain't a problem, really. Just helps prevent super abuse cases.