6) And also, try to achieve 12.5% haste. If you plan to run raids with either boomkin, spriest or shaman willing to pop +5% haste totem, you can get just 7.5% and then go for mastery. Otherwise, just reforge to get to that 12.5%, it helps a lot.
Most of what you said is fine, but this is flat wrong, and I wish people would stop saying this. First of all, Haste is multiplicative, not additive. If you have 3/3 Darkness and the 5% Haste buff, you only need 4.022% Haste (or 516 Haste Rating) to achieve 12.5% raid buffed, not 7.5%.
Second, and more importantly, going straight Mastery past that point is BAD advice, and this is from someone who generally prefers Mastery to Haste. The usefulness of the two stats at that point is pretty close to even and their value depends upon whether you're raiding 10s or 25s, what your role is, your mana situation, and even the specific fight. For instance, if you're working on Chimaeron, Mastery is borderline useless and Haste is extremely valuable; on a fight like Cho'gall, where there is plenty of time to top off and the healing intense portion is constant increasing damage, I find Mastery very useful and Haste rather meh. In fact, if one is struggling to heal up Caustic Slime targets on Chimaeron, or going OOM on Cho'gall as progression fights, some reforging for one or the other is a consideration.