i will try the HP EV this time as you say..
BRIGHT POWDER for my Volcarona helps me a lot,, since most attacks that she cant resist have decreased accuracy, like Hydro Pump and Stone edge
i might also dont want to add another focus sash since i already have two of them.
DRY SKIN gives me an immunity to water attacks too, additionally helps my AcidPunch to recover quickly if my opponent tries to hit my Volcarona with water attacks i'll just switch to Him, also Its a good counter pokemon for GRENINJA Users.
for status I also have MAGIC BOUNCE Carbuncle,, and for Milotic i think your right to just add my defense EV to other attributes
and for HAXORUS, he's my lead pokemon and i dont want to switch him sorry,, he can still swept 3 pokemon even having 1HP left.
Thanks for your help Asha