In a nutshell Shield stacking... well a walnut shell.
I have been wracking my brain trying to understand the reason for this push and then realized it was connected with the shield stacking problems people have been having with sorcerers. With Surge heal built in and shield stacking sorcerers would be able to recover large amounts of health from huge groups trying to kill them.
Problem seems strongly connected with Shield stacking as sorcerers will end up depending on a build where they can keep shields, recover health and magic while their pets do the damage as they throw AoE around groups.
Theoretically it would make sorcerers a huge problem as regular things like crit and such don't effect shields hence the push for GCD on Surge.
Really though this is entirely ZoS fault anyway, with the poor decision to nerf light armor to become the most weakest armor in the game and nothing to compensate it (Even spell penetration is a whopping 900 points for 5 seconds) people are now relying on shields like Angels with A.T fields from Neon Genesis.
Really the only way the solve this is to increase spell power on light armor, give it more spell penetration like before to make it more attractive for casting magic and scale shields to percentage of maximum health or certain percentage of maximum magicka instead of total maximum amount
The only other solution, which I bet ZoS will take is take cricket bat to Hardened ward and cripple the amount it shields you along with other shields.
Eitherway I see some really dark design choices for Sorcerers, as prove through this games life span and the life span on PTS.
Very depressing.