It still isn't imba as we think but GC stated here that BV bonus will also effect Shield of Righteousness. Also I still think that 10% seal bonus should be like 20% to get more benefit than t7 2pc bonus. This is not the case of this topic though.
The way we want 4piece t8 for Prot paladins to work is that the Shield of Righteousness also benefits from that extra SBV. We can try to make the tooltip a little cleaner.