For personal reasons, I opt not to upload any SavedVariables folders or files.
It looks complicated to begin with, I know, but play around with it a bit and you'll get the hang of it. Try several different buffs to watch, learn when something shows and when it doesn't, and get the hang of the "inverted" function (which is what you want for warning when something is missing).
What I can do, is give a detailed description of how I'd set up a "missing Earth Shield" display on my shaman.
- Type /powa in the chat window to open the Power Auras interface.
- Click the "New" button.
- Check "Text Aura" and type in "Earth Shield missing!" in the below editbox.
- Click the "[T]" button and select "Starcraft-Normal" as the font.
- Adjust size and positioning until I'm satisfied (if the text doesn't show up, make sure you press enter after entering "Earth Shield missing!", and if it still doesn't appear, left click the questionmark icon in the main Power Auras interface).
- In the Activation tab, select "Buff" from the dropdown list, and in the stacks editbox, type in ">2".
- Quick recap here - the addon is currently set to show the text when the buff is present and has more than two stacks remaining.
- In the editbox below the dropdown selection, I fill in the buff name to look for - "Earth Shield".
- I check "Invert", meaning I put a big "not" in front of the conditions I entered above.
- Now the text will show when the buff is NOT present or when its stacks are NOT higher than two. This is what we wanted.
- The rest is optional, but I tend to make sure there's a cross in the checkboxes for "Resting", "Mounted", and "In Vehicle", meaning Power Auras won't display the text when in a town or inn, on a mount, or in a vehicle (such as in the first section of Ulduar or the third phase of Eye of Eternity).
- I also make sure there's a check in the boxes for "Alive", "In Party", "In Raid", and "Cast by me". This means that, in turn, the text will only show when you're not dead, you are in a party or a raid, and when the Earth Shield in question is from you and not some other resto shaman.
- Since Restoration is my secondary spec, I also make sure the checkmark is only for "Spec 2", and not "Spec 1".
- After that, I just close the Power Auras interface, and I'm done.
Hopefully this has been helpful to you. There's a lot more Power Auras Classic can do for you - play sounds, animate graphics, show duration of buffs and debuffs - but I'll let you experiment with that on your own.