I’m not sure how I missed this, but at one point or another the Glyph of Shackle Undead was changed from extending the range of the spell to effectively giving it more spell hit. Good stuff!
I spent some time on the laggy-as-hell Player Test Realm during one of the all-too-frequent beta realm crashes (yes, the lag on the PTR is much worse than on the beta realms). Nearly an hour was spent spam shackling mobs while half naked (no +hit gear). After over 200 casts, I had zero early breaks and zero resists with Shackle Undead.
The wording on the glyph is quite unclear. It reads “increases chance of success for your Shackle Undead spell by 8%.” I interpreted that as meaning an effective increase of 8% spell hit for that particular spell. To understand what 8% extra spell hit would do to the spell, you much first have knowledge of how spell hit affects it.
When Shackle Undead is cast on an undead mob, there is an initial hit check, just like with any other spell. The spell will either shackle the mob or it will miss. The chance that the spell is initially successful is based off of your Spell Hit stat and on the difference in level between you and the mob.
- As things are now, if you are the same level of the mob, you have a base chance of 4% of missing with your spell.
- If the mob is two levels higher than you, your base chance of missing is 6%.
- A three-level difference between you and the mob means a 17% base chance of missing.
Note: We are speaking strictly of mobs that do not have crazy magical resistance stuff going on. Those creatures are few and far between, and are rarely undead anyways.
As things are right now on the live servers, your chance of missing can be reduced with spell hit down to a minimum of a 1% miss chance. You will always have a 1% chance of missing regardless of how much spell hit you have.
But! In patch 3.0.2., and WotLK, that previous irremovable cap of 1% miss chance will be gone, making it possible to stack enough spell hit to land your spells every single time. Yes, you too can have your very own 100% hit chance with spells!
With Shackle Undead, the real wrench in how it works are its “pulse resists.” After successfully landing the spell, there will be periodic resistance checks to see if the spell breaks early. On each check, the chance the spell breaks early is equal to your initial check to see if the spell will miss.
I was really interested in seeing if the glyph solely affected the initial hit chance, or if it affected the pulse resists as well. So, I couldn’t just sit there and spam Shackle Undead on mobs. I had to cast Shackle Undead, then stand around twiddling my thumbs waiting to see if the spell would break early. I didn’t let each and every cast of it go the full 50 seconds, as the chances of it breaking early on each pulse resist are equal, and I wanted to get a good amount of data on both the initial hit chance and the pulse resists.
From my 242 casts on mobs of the same level as myself, I had zero misses, and zero early breaks. I had zero +hit from gear/talents (except for the glyph). I would have tested further, but (surprise!) the server crashed.
I should have missed about 10 times with the spell, and seen even more early breaks. Thanks to the Glyph, I had at least enough spell hit to overcome my base miss chance of 4%.
I know that my testing of the Glyph of Shackle Undead was limited, and more research would be needed to definitively say that it functions as a straight 8% increase to hit chance on the spell. However, I feel it fair to initially conclude that it works as a bump in +hit on the spell (on both the initial hit check, and on the pulse resists). Whether or not it is +8% as the Glyph tooltip implies remains to be seen.
To the best of my knowledge, there are not any raid encounters with undead mobs more than 2 levels higher than us (Wowhead agrees). In Caverns of Time – Stratholme, there are some undead mobs at level 82 that can be CC’d. So, for instancing/raiding at level 80, we only need 6% spell hit to land Shackle Undead every time.
Why, then, does this glyph appear to give 8% hit instead of 6%? Does it intend to help us in leveling as well as raiding? Who really relies on using Shackle Undead a lot while leveling, and often fighting mobs 3+ levels higher than themselves?
It’ll be interesting to see if there are any raid encounters where Shackle Undead is necessary for crowd control, actually making this glyph useful.
If you want to know more about how spell hit (and spell resistances) work for priests, I previously posted about it here.