There has been a huge change in the way to calculate the bonuses from +healing and +spelldmg gear. Especially for healing classes this will become a huge change.
Right now many healer use low level spells with great gear to safe a lot of mana. A low lvl spell reveives the same amount of +healing and +spelldmg like a high level spell.
Blizzard felt that this was negative for gamebalance and so in TBC they changed the way to calculate the bonus from these stats.
The new way to calculate the bonus is: ((spell level)+6)/(player level)
To give a good example of what this means i quite a post out of the US-Forums from Drysc
Take the Priest spell Heal 2 as an example:
The spell is learned at level 22, and the base points for healing on the spell keep increasing until level 27. So, level 27 is considered the spell’s max level in our calculation.
This system gives an additional 6 levels of slack before applying any penalty to casting Heal 2; so, players up to level 33 can cast it with no penalty.
In this example, we will use level 34 (one level past the cast level of the spell) as a starting point.
The bonus from +healing is multiplied by this ratio: ((spell level)+6)/(player level)
That means the level 34 player only gets 97% of the normal bonus from +healing items when casting Heal 2. A level 60 player would only get 55% of the bonus, while a level 70 would get 47%.