The spell hit table is actually quite simple: the dice behind your character's stats roll to see if you hit or miss, and then roll again to see if you critically strike. There's no seeing if the mob dodged, parried, or blocked you. If you can see them in line of sight, you could possibly hit them. Things can absorb your attacks, however, and reflect your spells.
You probably learned as you were leveling that very first time that you missed some of the time, and you missed more often against higher level mobs. There is a natural miss chance for a spell to hit based on level difference. The point of hit rating on gear is to cover this gap so you never miss.
Spell hit in Mists of Pandaria
One twist to hit in MoP is the inclusion of expertise rating as spell hit. This allows a warlock to reforge an item that already has hit on it into expertise rating, which adds more spell hit. It also allows as warlock to take advantage of specific racials when wielding the correct main-hand weapon.
The caps are different for PvP and PvE activities. In endgame PvP, it's assumed that you're going up against players of the same level as you (6% hit). In PvE, it depends. Heroic 5-man mobs are considered to be +2 levels (12% hit); raid bosses are considered +3 levels (15% hit). Challenge modes have raid-level bosses and do not adjust the spell hit of a character in the ilevel changes.
How much rating is that? In previous expansions, the hit rating grew with the gear ilevel, and scaling helped keep the percent the same. So you got oddly specific numbers like 1742 rating for your hit cap and freaky decimals for 1% (102.47), since it had been the same 17% raiding hit cap since forever. In MoP, the hit chance was redone, so now we have a more memorable number like 5100 for the hit rating cap and it's 340 per 1%.
The hit cap is a hard cap; that is, any rating over the cap does nothing extra for you. The main headache about spell hit is due to the hard cap fact. Soft caps -- like haste plateaus -- are points where "this much" rating is highly desirable, but going over will still provide benefit, if less importantly.
Should I cap my hit?
The short answer? Yes.
The long answer? Being hitcapped guarantees that every damaging spell you complete a cast for will, barring absorption, deal damage. So to put it simply, missing hit is possibly missing damage done, and you should cap your hit as best you can.
But I can recast the spells I miss! Sure you can. But wait, do you see that floating combat text there?
That's a soul shard wasted because your Haunt missed. That's your Soul Swap only applying Unstable Affliction and Corruption because Agony missed. That's Agony or Doom falling off because you tried to apply it at the last second and you missed. That's your Wrathguard missing because he inherits your hit percent. That's your 500k Chaos Bolt doing zero damage because it missed.
But I see top warlocks with ~12% hit? First, the Armory is not displaying spell hit gained from expertise correctly. If you look on your paper doll sheet in game, your spell hit will correctly show for its percent value as your hit rating plus any expertise rating you have. Second, make sure the warlock in question is wielding an expertise-racial weapon to make up for the missing hit.
An excellent example is Gobuchul, aka Zakalwe from the warlock Elitist Jerks forum. As of writing, his hit rating is 4334; add in 428 expertise rating to get 4762 rating, which when divided by 340 (1%) is 14%. He's an orc, which has the expertise racial for wands, and he's wielding a wand, which counts for the fist weapon of the Axe Specialization racial. Thus, even though the Armory says he's at 12.75% spell hit, he's actually hit capped.
But I gain 400 DPS from extra X stat by reforging under the hit cap! Ask yourself this: am I at that level of play where 240,000 damage over the course of a 10-minute encounter is going to matter? (Honestly.) Would you gain more DPS from adjusting your spell performance than from adjusting your gear for a 0.5% DPS stat gain? (Probably.)
Now, this doesn't mean you need to be super precise about the hit cap. I think being within a reforge or a hybrid gem of the hit cap is an OK under-cap number to be at. At least then you tried to make it work.
Is it interesting for tanks to balance threat (hit/expertise) with survivability (dodge/parry/block)? Maybe. I know some tanks take pride in how much DPS they can put out while also surviving the huge hits to the head. Others simply don't care.
Is it interesting for healers to balance mana regeneration (spirit) with throughput? Mana regeneration is a comfort thing, which can vary from healer to healer, but I think they all eventually end up at around the same number per class.
Is it interesting for damage dealers to balance hit rating? If you're under hit cap, you "lose" because you need more of it. To paraphrase Ghostcrawler, if you're over cap, you still "lose" because now you have useless stat sitting around. There is seemingly no win scenario unless you manage to hit that Goldilocks number that is the hit cap. So no, it's not interesting for damage dealers because it's not fun to balance.
Is hit a necessary stat for damage dealing gameplay? In World of Warcraft, yes.
In games like Guild Wars 2, you can physically move your character out of the way of a spell or a melee attack. Similarly, your character can misfire by facing or aiming in the wrong direction. There's no real point to a "hit" stat there, and indeed, Guild Wars 2's Precision stat for necromancers is more like critical strike for us WoW warlocks.
World of Warcraft, on the other hand, is still an old-school game at its core. We're just getting into moving while casting, and my Drain Soul will still channel as a target moves out of range or line of sight. Our gameplay is still very much rooted in invisible dice and our paper doll stats rather than in the animated space our characters occupy. So we still require a paper doll stat to counter our phenomenal cosmic powers.
Spirit and expertise
The spirit-to-hit change was a mistake. Now that it's here, there really is no solution that won't upset some major portion of players involved.
Holy paladins don't really care since they're the only intellect plate users anyway, and mistwalker monks might not care since the other two monk specs look for agility leather. Caster druids and caster shaman think it's a cool thing since it allows them to share caster DPS gear with healer gear instead of trying to gain two different sets.
But the duality of spirit as both a healer stat and a DPS stat runs into problems when you look at the cloth armor class. Removing spirit as a hit stat puts priests back at the difficulty of gathering two different sets for healing and DPS. Trying to fuse spirit and hit into one stat will increase the competition on gear to everybody. Whatever happens now will royally annoy half the clothies.
I also don't like expertise as spell hit. It's not as angering as a healer offspec needing on that hit gear you need for your pure DPS play, but it's still not a great solution for making hit interesting.
I don't enjoy having to open my melee stat pane to find my expertise rating number so I can add it to my spell hit rating number to make sure they equal out to the hit cap number. (The spell hit percent may update correctly in-game, but I do most of my gear management out-of-game with the Armory, which does not update correctly.) The racials-to-weapons spread doesn't make it better; at least draenei have it easy in that they always have that extra 1% hit instead of having to remember exactly which weapon is their race. Expertise as spell hit is more reforging leeway, but it's also more work to double-check myself when min-maxing my character.
We don't need more ways to express spell hit or mana regen nor even a fusion of the two stats, but a more efficient bridge between healer gear and caster DPS gear. I'd like to see what happens with destruction's Chaotic Energy and haste as the tiers go by and whether that could apply to healer mana regeneration. Then we'd just be left with the original predicament by Ghostcrawler: is hit an interesting enough stat to keep defending?
Blood Pact is a weekly column detailing DOTs, demons and all the dastardly deeds done by warlocks. We'll coach you in the fine art of staying alive, help pick the best target for Dark Intent, and steer you through tier 13 set bonuses.