Also, I don’t see why attacking with a Tier 5 bloodline ability should have a bigger bonus than a Tier 1 bloodline ability.
I don’t think anyone was suggesting that, at any point. The whole thing with the Bloodrank implies BLOODRANK, not Tier of Bloodline power. Therefore, if you have BR5 in the present you’d have a +10. In the one I suggested you’d have BR+Tier YOU were.
Sorry. Misread the Tier as tier of bloodline rather than your tier. Personally, I still prefer BRx2 but BR+Tier would work.