Simple skill idea for tanks/support

Primary ability(Q/W/E) - stacking shield. When pressed adds (20/30/45/70/90) shield. Cooldown 15-20 seconds. Can be stacked up to 5 times( example. at lvl 1 shield can be stacked to 100. lvl 2 : 150 etc.. ). cost 30/45/60/75/90 mana

have yet to think of a name but yer first time posting here so im not sure if this post is up to scratch but just wanted to share my idea