(What a boring title. Seriously, I tried to think of something clever, but I'm fresh out of clever this morning, so you'll have to settle for "thorough")
In my post regarding gems for priests, I tried to make it clear what your best choices are for each color slot. Essentially, if you want a red gem, your only real choice is spellpower, whereas if you want a blue gem, you can get spirit or Mp5. These are simplifications - each color is connected to certain stats, and you choose which of the stats you want from that color in various combos.
I bring this up because I don't think people truly recognize that Blizzard has designed much of the gear in a similar way - stats compete with one another for the same slot. I see a lot of questions in forums over which stat to prioritize, when in reality, you rarely have a choice over the appearane of a stat. If you are trying to prioritize one stat over another, you will probably have to be more focused on the ratio of the stat distribution
There was a discussion over on the plusheal forums regarding stat choice that left me vaguely frustrated and inspired me to post an explanation on this topic. I see too many people Missing The Point, so I'm going to give a very basic rundown of how stats on gear are distributed:
Item Level is an indicator of the summation of stat value. Each item is given a certain "budget". If you are comparing two iLvl 213 items, they will have the same budget, though their stat distribution may be different. One item may have more spellpower, while the other may have more intellect. In other words, the amount of the stat may vary, and therefore the proportion of the item's budget spent on that stat may vary between items of the same item level. The same stat is on both items, just in different amounts.
In general, all relevant caster gear will have Stamina, Intellect, and Spellpower on it. What WILL vary is the budget allotted to each of those stats in proportion to one another - i.e. the budget ratio.
In addition to these "ratio" comparisons, certain stats "compete" with one another for even appearing on an item.
Examples include: Spirit vs. Mp5 and Haste vs. Crit. What this means is that if you see spirit on an item, it is unlikely the item will also have Mp5. If you see an item has Haste, it will probably not have Crit.
This is the general pattern - here are the items that drop from ToC25 regular to give you an idea. Type in "cloth" in the "search within results" box to simplify it, and if you look through these items, you will see that the rules listed above apply.
Merlin's Robe has both critical strike rating AND haste - two stats that normally compete with one another for a slot on gear, and therefore rarely appear together on the same item. To balance this out, it has neither spirit nor Mp5. The same thing for Bejeweled Wizard's Bracers.
Off the top of my head, I cannot list for you other items that have both haste and crit, but that does not mean I am suggesting they do not exist. On the contrary, there are a handful of items that break the stat distribution rule of thumb. And because of that, they have always been in pretty high demand. What makes Merlin's Robe and the Bejeweled Wizard's Bracers especially enticing is that from what I can see on the cloth drops from ToC, none of the other items available at this item level break that stat rule EXCEPT for these two crafted items. (if you know of any others, please point them out to me!)
So, two major points to take away from this long-winded post.
If you are trying to prioritize one stat over another, how you do this depends on the stat. For instance, if you want more haste, you will usually be choosing haste over crit. However, if you are trying to pick up more Intellect over spirit, it doesn't exactly work that way - Intellect will be on all items, whereas spirit competes with Mp5. This kind of fine tuning is better done through gems.
If you want to say "screw you mana regen! I'm disc! I'VE GOT BUBBLES, gimme more haste/crit", you need to specifically seek out items that have both haste and crit on them, because they are exceptions to the rule, and not incredibly common. At current max gear level, your best (and possibly only) options are the two crafted items, Merlin's Robe and the Bejeweled Wizard's Bracers.