Are you healing with a macro and have accidentally been using the wrong rank shield perhaps?
3k+ spellpower as disc will certainly be more than 2k absorbs, im not fammiliar with WoL, perhaps thats your glyph of Pws you are looking at? or aegis proc? Or WoL does not record it correctly at-all.
Thats all I can think off, off the top of my head.
I have always used Wow-meter-online in wotlk.