Dictionary Time

Before I get into the swing of writing a guide, I figure I should define a few terms just in case readers don't understand them and run into these in the middle of a guide and go "huh?" They're pretty common in the theorycrafting community, but I don't know how widespread they really are outside of it.

Regen - Obviously from the root regeneration, when I talk about regen, I'm not just talking about your pure mp5, but your mana efficiency. In most times mana efficiency in regen models can be reduced to mp5, and these mp5 numbers are used to compare the efficiency of a talent or regen potential piece of gear with others.

Throughput - The amount your spells heal. Healing is a fun game of balancing throughput (output) and regen (efficiency), though the balancing gets easier the higher up in content you get. Throughput can be increased in two main ways: spellpower and haste. SP makes your heals larger, Haste makes the same spell hit sooner, which is an HPS increase. Crit is a strange beast. For single target healing, it is worth calculating in terms of HPS. For Holy priests, it is primarily a regen stat. I will go over this in more depth later.

HPS- Healing per second. This is just a measure of the amount of brute force healing you put out with a spell averaged out over a one second interval. A 1.5 second cast Flash Heal that heals for 5000, for example, has an HPS of 3333.3(repeating). AoE heals are averaged based on number of targets so their HPS is obviously higher.

HPM - Healing per mana. This is a measure of efficiency. Some spells sacrifice HPM for a gimmick, have conditional HPM (how many times PoM jumps affects its HPM), or have high HPM but can be more conditional to use than their less HPM counterparts (Renew is more likely to heavily overheal than its less HPM counterpart Flash Heal).

Item points and item level - These are concepts relating to gear, and are very important to gear modeling. Item level refers to how Blizzard puts stats on gear. We all know that gear from Ulduar is better than gear from Naxxramas, and the reason for this is that the gear from Ulduar is higher item level than the gear from Naxx (Naxx 25 gear is mostly item level 219, and Ulduar 25 normal mode gear is item level 226). What this means is that the gear from Ulduar had more item points to spend on stats than the Naxx gear. Each stat costs item points to put on the gear and when all the item points are spent, the item has been completely statted. For example, a point of mp5 costs around 2 item points, while 10 spellpower is 8.6 item points, and crit and haste are each 1 item point per rating.

This is important for certain types of theorycrafting, like stat boosts, as any stat boost you can gain from a talent, for example, is the equivalent of free item points since you get the stat without having to gear for it. For example, Holy Specialization is a free 5% crit on all holy spells (i.e. everything you'll cast as a healer). This is the equivalent of 230 crit rating, or 230 free item points that you don't have to put on your gear to hit the same amount of crit. Equivalent item points will come up on occasion in some math threads, but I'm not going to crazy with it, as it is only situationally useful to concept things in those terms.

DR - Diminishing Returns. There comes a point where continued stacking of a stat isn't useful anymore. You just aren't gaining as much out of having more of it. For example, when Disc hits its haste soft cap of 50% with Borrowed Time active, haste isn't as useful for Disc anymore; it isn't completely worthless it is just of less value. An example for Holy is crit. For an AoE healer, crit much past 30% gives less regen benefit that the 30% before it.