They are very expensive to invest, and provides as @TrueHiddenMist said, just a way to convert dead cards into 3-Damage.
IF, you instead build around using them all the time, you will have the same problem as Hawkeye: it will severely impair your board growth and will eventually made you behind other players in mid-late. Unlike Hawkeye, you cannot collect loose arrows with your quiver to thin your deck; these two cards (among other questionable hero events will be meddling around for the whole match).
Also, they are restricted; Side Holster is required if, you are planning to get another weapon.