Not sure how much you know about in game mechanics, but it's not a spell you want to "spam." 1) it does no real damage 2) it's only utility is that it freezes mobs for a short time. There's a thing called diminishing returns however. If you were to spam it essentially the mobs would become immune right away to your "freeze." The ring's purpose is to cast a reflex spell in the event you take damage in a large chunk where 1) you might not be paying attention or 2) your reflexes are too slow to react accordingly. It essentially buys you a short period of time to regroup and when paired with an item like ancient parthan defenders gives you significant damage reduction for a short period of time depending on number of stunned/frozen mobs within 25 yards of you. Long story short the in game programming is correct. If you are wearing Halo and have frost nova on your bar, the logic is coded as such to let the ring trigger the frost nova on its own so that you maximize the diminishing returns thus maximizing the utility of the ring and the frost nova spell.