@Riot: as a former conqueror user, is it intentional that lethal tempo doesn't trigger on shields?

Seems kind of silly. I have to work my whole playstyle around how and when I will damage a champ, since it has a 1.5 second delay. But if the champ has a shield, I have to get rid of the shield first. I can't use a long range ability to trigger lethal tempo before getting into melee range... They can basically nullify my rune with overheal.