well, i wouldn't say it's a completly bad idea, except for you should tailor your ev's to suit the role you want the victini to do.
so if you want a victini that uses special attacks you wouldn't put any into attack since you won't be using your attack stat. if you want something to just take a beating and stall your opponent you'd go for def/s.def/hp.
although with 85's in 5 stats you are wasting an extra stat point you could get into one of them because you get one stat point for every 4 ev's in a stat up to a maximum of 255 ev's in a stat and 510 ev's total(so 252 is the max usefull value).
for example, i wanted a fast and deadly gengar. so my gengar has 252 speed, 252 s.attack, and 4 hp