Tahm Kench W bug?

The damage from his W (Devour) can be negated in full by a champ with shield or an hourglass. If the shield is hit as soon as the leave it seems to act like the champ was never in and not take damage. Also hourglass being used as soon as spit out will negate the damage caused by it as well. If this is not intended it needs to be fixed and changed it has cost me a couple games in ranked.