Grid to the Rescue
IMO Grid and Clique are the essential tools for successful healing. Even if you're a purely DPS-minded Shaman, having these installed is highly recommended, and your raidmates will love you for it.
- Open Grid's config window: /grid config
- Open Status > Auras
- Type in a new debuff and hit enter: "Frost Blast" (without quotes)
- Find the new debuff in the Auras list, change the color to a blinding bright red
- Also make the priority 99 (meaning topmost priority)
- Open Frame > Border
- Check your newly-added Frost Blast debuff to enable it
Don't Stand So Close to Me
Also, if you have Deadly Boss Mods installed (which of course you do!), type /range and you'll see a handy little display of those within 10 yards. Move accordingly.