I have to agree with Eddy Wang here since I feel the Heart Pierce has more KB's than Blood Drive and gains a parry and a Teleport vs BD'S +4 Restand with only having 13f mids and the ability to control speed of projectile.
The projectile is very good but costs a bar to slow or speed it up, the BF4-AMP only gives back 3.4% health compared to the BF2-AMP that gives 7.6% back. I wouldn't waste a bar for 3%.
The Sciphon only gives 4 frames of advantage on hit but her mids are 13 frames allowing the opponent to beat her out with moves that are 8f startup. I'm sure block still takes a frame.
Parry is definitely strong considering you can cut strings of short with it linked and hold it forever. It also has a Krushing Blow and it counters throws, highs, mids and overheads but gets beat out by lows and projectiles. I feel the Parry alone is enough for me since it looks like block and there is no flashy animation to differ the two.
Teleport is also a great tool to gain space and regain neutral or esacpe pressure or corner.
I think they are both viable but I prefer Heart Pierce over Blood Drive.