Focus is to the left of the target frame. The target's target is to the right of the target which is the focal piece in the preview image. The numbers are simply health percentages. The target has no percentages. Instead, the top blue bars each represent 10% health, so once your target hits below 100% one bar goes away. The bottom orange bars represent 1% and will deplete faster, kind of like the hour and minute hands on a clock. On hover it will change to power. This is to be a pure raid environment (PvE) UI, so having power display constantly on the target frame doesn't make much sense to me and isn't particularly useful. I did this as a concept and to differentiate between each frame more easily.
I need some help with ideas for the player frame. Preferably, I would like to show either health and power as a percentage text or health as a bar with power as a percentage text.
In Raid-Environment there are quite some moments you might need target's power, though. Thinking of Deathwhisper (2nd boss ICC), Saurfang...
Anyway, loving your concept!
I'm a warrior-tank, so I would want both, health-bar and -text on my player-frame. No need for power-text, though. But when I'm on my Resto-shaman, mana is crucial, so I think you will need to apply both.
I would go with your HP-bar-concept for player, too, but add a percentage-text atleast.
You could make a "big-bars-only" approach for power, with text. You could size them smaller as the hp-bubbles.