the best way to go about doing Cow Runs are to do them in groups if possible. If you're playing solos, try to use abilities that have a lot of Area of Affect damage. There are a LOT of Hell Bovines in the level and they like to crowd around you and try to trap you. Frozen Orb (Meteorb Sorceress), Blessed Hammer (Hammerdin), Lightning Fury (Javazon), Poison Nova (Poison Necromancer), and more abilities like those can do wonders against the Hell Bovines.