When people talk about raid healing as a resto druid on forums, those people are almost always playing the content in the role of raid healing 25 man content. In that role, stacking haste over mastery makes the most sense, while your dropping hots on your dps and healers, you want the most ticks as possible. Almost every guide says that is THE only way to heal in a raid, but i beg to differ.
With great success i have been running 10 man regular raids, with out stacking haste to the magical 1600/2200 mark, how? Tank healing and dividing up hast and mastery. Our "horrible" mastery is useless in the role of healing 25 people with one HoT, but in the role of healing a single tank (hopefully a pally) we can use the true potential of our mastery. lifeblooms, stacked with our other two HoTs, regrowth and and rejuv, offer maximum healing per tick. ideally you would stack haste to the 1600 mark, with buffs, and then focus on mastery. this gives us the most ticks off of our hots, and allows us to gain 25% or more healing from each with our mastery. This set up also allows us to cover our group with wildgrowth and rejuvs when needed, as long as the player makes sure to STACK his spells, casting them one at a time wastes your mastery.