Let me explain how the target auras work in the HUD (the same applies to the target of target, as well) as well as the aura display in general.
The overall organization of the aura display is as follows...
- The full list of buffs on you appear in the aura list at the far left edge of the display. This includes your self-cast buffs, party buffs and raid buffs and comprise all of the auras on you that are to your benefit. Any buffs you have cast on yourself are highlighed in green.
- The complete list of debuffs on hostile targets (or buffs on friendly targets) appear in the aura list on the far right edge of the display. This includes the auras you have cast on the target as well as all party or raid auras on the target. These comprise all of the auras on the target that are to your benefit. Your buffs on the target are highlighted in green and your debuffs on the target are highlighted in red.
- The auras *you* have cast on the target appear in the center of the HUD immediately below your casting bar. These are the spells that are active on the target, to your benefit and cast specifically by you.
- The complete list of buffs on hostile targets (or debuffs on friendly targets) appears on the right side of the HUD either directly below the target's name or to the right of the health race bar. This is the complete list of auras on the target that are to your detriment (and likely dispellable). The auras are usually highlighted by their type (blue for magic, etc.).
- Debuffs on you appear on the left side of the HUD either just below your name at the top left of the HUD or just to the left of the healthrace bar. This is the list of all of the auras on you that are to your detriment. The auras are usually highlighted by their type (blue for magic, etc.).
So in a nutshell, the list of all buffs to your benefit and cast on you appear on the left edge of the display. The list of all buffs to your detriment and cast on you appear on the left side of the HUD, the list of all auras you have cast on the target appears at the lower center of the HUD, the list of all auras to your detriment and cast on the target appear on the right side of the HUD and the list of all auras cast on the target to your benefit appears on the right side of the screen.
Simplifying that even further... all of your auras are on the left, all of the target's auras are on the right. All auras to your benefit are on the outside edge of the display. All auras to your detriment are on the outside edges of the HUD and the auras you placed on the target are at the bottom center of the HUD.