One of the things that makes a vamp build so nice is the ability to heal. Any rank of Potency cuts our heals in half. So, it doesn't make much sense to take the 50% heal nerf with only a 5% damage boost. As far as R2 Fever, it's more of a personal choice. Higher ranks give you a slightly higher chance to generate blood and a higher hit when it pops.
Level 51 Demonologist
Level 46 Full Healer
Level 46 Psionicist Incarnation
Level 2x Bard Incarnation