Staling Weavile is made to take advantage of its ability, pressure. With pressure any move used against Weavile, or in general by the opposing team will lose 2 pp instead of 1. Combine this with spite, protect and substiture, you will be draining their pp fairly fast. Weavile itself is a glass cannon so handle with care. The EV spread is given so it can still remain fast, and with fake out, still deal a good amount of damage.