The alpha test of Wrath of the Lich King has apparently kicked off and there's lots of interesting info flying around (probably with some fakes mixed in). One seemingly minor point that has flown under the radar is a nerf to several talents that affect spell hit rating. Arcane Focus and Shadow Focus currently have five ranks and boost the spell hit numbers for Arcane Mages and Shadow Priests by 2% per point, to a max of 10%. The talents are rumored to be nerfed to three ranks at 1% per point, with a supposedly compensatory bonus of 3% off the mana cost of the respective spells. Frost mages know this particular nerf well, since elemental precision used to be 3 ranks of 2% per point for a total of 6% hit (for frost only), before changing to its current 3% hit, 3% mana cost for both fire and frost (ensuring that almost all fire mages somehow find three points to spend in the frost tree).
For those who don't know how Spell Hit calculations work, players start at 96% hit against even conned targets and cap at 99%. This means that 3% hit from talents is sufficient to reach the hit cap for even conned mobs, beyond which additional spell hit rating offers no additional benefit. You will need an extra 1% (4% total) to cap against mobs one level higher than you, and an extra 2% (5% total) to cap against mobs two levels higher. So why, you might be wondering, was there a talent offering 10% spell hit? Mobs that con 3 levels above you, which includes all raid bosses, require a whopping 16% hit to reach the cap, and, for most DPS casters, spell hit rating is more valuable point for point than any other spell stat (including spell damage) until you reach that cap. The implications of an extra 7% spell hit are significant - for a level 70 character, that's 88 points of spell hit rating that can now be replaced with bonuses to other statistics.
Why make this change?
Like I said, Elemental Precision used to grant larger amounts of spell hit until it was nerfed (back in 2005 or so, if memory serves). However, the other talents were in the game at the time and are being nerfed only now. Perhaps the specs in question are doing more damage now and thus fell within the sights of the nerf gun. Perhaps, with the amount of spell hit rating required to get 1% spell hit going upwards at level 80, a 2% bonus per talent point was deemed too great, especially since the talents in question are low on the talent tiers and often taken anyway to unlock more advanced talents.
However, there is another, intriguing possibility, on which I will now engage in some completely baseless speculation. It's been stated that Blizzard would like to do a better job with tiered rewards in the new expansion - as they described it, the elite arena gear with high rating requirements will be comparable to the current 25-man raid, the low end arena gear with low requirements will compare to the current 10-man, and the gear available in battlegrounds for honor alone would be comparable to heroic five-man loot. What if the difference between the gear quality was primarily spell hit value?
Even Heroic-mode 5-mans do not currently expose players to "boss" level mobs (which, again, will always con +3), so spell hit rating could, in principle, be almost absent from 5-man gear, as players of most caster classes would be able to get the hit rating they need from talents. Now imagine that the corresponding 10-man upgrade includes similar raw damage but ALSO includes spell hit, and that the corresponding arena upgrade again includes similar raw damage but ALSO includes resilience. Then imagine that the 25-man/elite arena upgrades contained MORE of their respective stats. Suddenly, you're looking at a system where there ARE still substantial upgrades for trying the elite material, without requiring Blizzard to cap non-raid/arena gear advancement. The spell hit on raid gear would not be wasted either - that extra rating would allow raiders who hit the cap to spec out of their respective spell hit talents, giving them more talent points to play with in their builds.
Of course, the question is whether Blizzard would actually be willing to remove some of the bribe factor from raid/arena loot (i.e. you'd still be snagging upgrades, but the upgrades would be focused on stats specific to that activity and thus you wouldn't be THAT much comparatively better than a non-raiding level 80 at, say, daily quests). The downside from Blizzard's perspective is that better bribes might otherwise lure players into harder, more time-consuming content. I suppose time will tell, and this is, as I've said repeatedly, all pure speculation on my part. I just think that the potential for this kind of parallel advancement offers some intriguing new design space that didn't exist in WoW 1.0 or TBC.