Why nerf heal and shield power when shield duration nerfd?

I believe nerfing heal and shield power just negates anything that a support can do unless you want one to go AP/with just ardent? unless you are playing a tank that can just engage and run away. I play some champions that RELY on heal and shield power to do anything because in this meta right now, in my elo, I feel like my team just gets run down so easily without shields or heavy peel from supports. What is the point of having a shield if it lasts not long when a assassin can delete it in 1.6 seconds?