Arcane ward is awesome. It's also turning into a necessity because if your opponent is ruining them then you must have either decoy, seeking dispel, or another arcane ward to get rid of its target, otherwise it costs you two dispels. Cheap nullifies are not the best use of them as they trigger on your own spells too. But fir keeping an investment around longer than intended they work great! I'm talking about cobra reflexes or any of the damage barriers, force crush, or force field, any of those big defenseless enchantments that you might not have wasted the mana on in other cases. I try to pack at least one. And a decoy just because the target line is so specific they are hard to get rid of.