I have not seen it yet displayed elsewhere (but have to admit that I did not check for very long...), but I noticed something:
Starting with the common knowledge: with the patch 2.3 many +healing items were upgraded to include +spell damage (in a ratio of about 33% of the +healing seems to be the avarage on both my resto druid and my SP). So far, probably "old news to all".
BUT, as my resto druid happily found out yesterday evening (he is enchanter too) that at least some of the +healing enchants give +spell damage too. I noted this to be the case at least for the +20 healing on rings (which now adds +7 spell damage).
I failed to check (the realisation of the scope of the change just hit me this morning after my first coffee) whether this would work for all other +healing enchants and glyphs such as the +80 healing on weapon, the healing on gloves and bracers too (for new enchants). I did not that the (already) existing enchants on the equiped gear for these enchants did not contain the extra spell damage (I will log in on my enchanter later today to see if ALL new to be set +healing enchants now contain the damage part).
The point of this being: would this change not simplify the life of a levelling shadowpriest (mine being only 48 atm). This would mean that your healing gear might actually still show a very decent number of spell damage and to certain extent eliminate the need for double gear?