@Meddler: What is your stance on delayed-activation shields for fighters/juggernauts?

More Champion Concept design questions.

My current juggernaut Champion Concept uses the following ability for a PbAOE and delayed shield skill:

W - Dark Resolve After a 1 second delay, Celes releases a burst of darkness around her, dealing 70/100/130/160/190 (+0.8 bonus AD) physical damage to all nearby enemies (300 range). If an enemy Champion or large monster is damaged by Dark Resolve, Celes receives a shield for 4 seconds that absorbs up to 80/110/140/170/200 (+8% of maximum health) damage; this shield's strength increases by 1% for every 2% of Celes' missing health.

Maximum shield strength: 120/165/210/255/300 (+12% of maximum health)

The obvious downside to this shield is that it takes a second before it actually kicks in, and if you don't hit anything with that PbAOE damage, you get no shield at all. But if you DO get that shield off, it's meant to be super-strong. (I probably have the values wrong.)

Would this be acceptable for a juggernaut Champion, or is it too clumsy or detrimental to the player?

For more context: http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/YJA491Te-celes-the-dark-crusader