FotM's Shield Explosion Mechanic should work like Ivern's E
The shield is really far too weak to last 4 seconds. Either lower the duration of the shield (so it's more likely to explode as less time to break it), do that and make it always explode after the time (2 or 3 seconds) or just have it always explode.
Or, increase the value of the shield and lower the amount it slows or something. Because right now I can't remember EVER getting to use the slow on the shield explosion.