Paladins sure get lots of Bubbles. Well I’ve had a change to try Sacred Shield some. It pretty much does what it says. Best i can tell and looking at the combat log on proc it absorbs up to 500 damage then fades away till next it procs which cannot occur more than once every 6 sec on damage. Its a Shield that looks like a somewhat shiny bubble. Sometime can be a bit hard to see it as the tank tanking when a Holy drops it on you, but its there if you refocus.
Anyway this doesn’t seem all that great as a spell for Protection, though it has some uses. Its seems more for Holy Paladin to use and to land it on the Tank or the one taking damage. It absorbs some damage going to the tank as they take damage if and when it procs and it seems to procs often which increases the critts of the caster of the spell Flash of Light as the tootip says. As a Protection the Flash of Light part is not of obvious benefit if your Tanking or if self casted in cases without another Paladin (Holy) on a 5 man run per say. But the damage shield has some uses in absorbing some damage in places where you have lots of AoE action. So some situational uses.
I asked a Holy Paladin on one my runs how it works for him and best he says he keeps it up on the tank as its free Flash of Light as it procs about 4-5 times over the duration of the spell. Its not great but every bit helps out he says.
Using it as a Protection I don’t really find it all that useful especially when soloing as often I’m blocking all the damage and in cases where I am doing that this spell is barely use full. In some massive AoE it can be useful some where you may have lots of mana to burn and lots of stuff hitting you all around which adds up. It has some uses, buts its very minimal soloing for a Protect and not usually worth using usually for a Protect. It also cost a bit of mana for a Protect to use with very minimal benefit.
I can only maybe imagine some Protection Paladins that somehow may have to off-heal in large Raid for some reason using it maybe to increase their Flash of Light critts maybe in rare situation having to heal. But with the mana cost a Protect already don’t have enough mana pool as it is to keep casting huge mana cost spells. I personally don’t ever heal so I can’t say beyond that personally as I rather DPS if anything. Now if your going to pull 10+ mobs to AoE it does have uses as you’ll have more mana than anything with BoS and you’ll probably be taking some degree of damage and it can only help. I’m kinda wondering where Rank 2 of this spell is as well.