It's really useful for chasing as well as running away. Oh, they leap in? Well, now they have decreased movement speed, and you still have increased movement speed. It's worth noting that the Focus #5 can only Chill one target (unless you also blow a utility skill), while the Warhorn combination of #3 and #5 allows you to keep packs of enemies snared.
I personally like doing Dagger/Dagger with Axe/Warhorn over the other options. The Focus is nice, but I just prefer the Warhorn, with it's interrupt and how well it helps kiting multiple targets.