On May 28th, FinalBossTV did a bunch of Ignore Pain testing on his Twitch stream. I was able to get on for part of it and he tested a bunch of questions I had. Here's a link to the stream. The Protection Warrior stuff starts at the 4 hour mark:
Here are some ticky-tacky details about it:
1. Ignore Pain was not being calculated correctly a couple builds ago
There were some bugs with IP values a couple builds ago for characters with less than 100% health. For instance, in this recent FinalBossTV Prot Warrior youtube video (https://www.youtube.com/watch?v=5ceIKQoAMX0), the IP values he's generating while in combat with the raid dummy around the 20:40 mark vary randomly and are much lower than they should be. So don't base theorycrafting on videos or logs from builds older than this week's (May 26) beta build.
These bugs have been fixed. If you're looking for a video of IP in action in a build that doesn't have these bugs, watch the FinalBossTV Twitch stream I linked above.
2. Ignore Pain is modified by your Versatility value
Versatility increases healing, which includes absorb values, which includes Ignore Pain. If you're calculating your Ignore Pain value, don't forget to multiply by 1 + your Versatility percentage from your character screen.
Versatility also increases the damage you deal, but it doesn't affect your attack power, so that aspect of Versatility doesn't change your IP at all.
3. Bonuses to IP% are multiplied separately, not added and applied at once
This is how all percentage bonuses in the game work, but it's worth restating. There are several bonuses that increase IP's value by a percent - Dragon Skin (up to 6%), Indomitable (25%), Never Surrender (varies), Dragon Scales (60%), and Versatility.
If you have 17.4% versatility, say, the formula for how those bonuses affect IP's value is this:
15 * AP * 1.06 (from Dragon Scales) * 1.25 (from Indomitable) * 1.174 (from Versatility)
Not this:
15 * AP * (1 + 0.06 + 0.25 + 0.174)
4. At level 110 with blue dungeon gear, IP's base value is about 20% of your base health
Here are some stats of a level 110 Warrior in blue dungeon gear:
Health: 1,865,820
Attack Power: 19,379
Versatility: 17.42%
For that character, who we'll assume has maxed Dragon Scales on their artifact, their untalented, unmodified IP is 15 * 19,379 * 1.1742 * 1.06 = 361,802, or about 20% of their health.
5. The absorb value shown in the combat log is 90% of the calculated value
IP "ignores 90% of the next X damage you take". The combat log event for applying IP shows how much damage your IP will eventually absorb, which means it shows 0.9 * your calculated IP value.
For example, when the 110 character above casts IP for 361,802, the combat log shows him gaining an absorb of 325,621. These pictures show the buff tooltip and log event for the same cast:
6. The 25% bonus from Indomitable is shown in the buff tooltip, but not in the spellbook tooltip
Here's a minor one. When you mouse over IP in your spellbook or mouse over the active IP icon in your buff bar, it shows the calculated IP value. However, if you have Indomitable, the benefit from it isn't shown in the value in the spellbook tooltip.
7. The bonus from Never Surrender scales linearly
We already knew this, but it's worth mentioning again for those who don't know. With NS, the percent bonus to your IP is equal to your percentage missing health:
IP value with NS = Base IP Value * (1 - current health %)
So, if you have 75% health, NS increases your IP value by 25%. If you have 20% health, NS increases your IP value by 80%.
8. Ignore Pain's maximum shield is equal to 2 * the value of your most recent IP
We also already knew this one, but the video confirmed it, and it's worth knowing. Here's Celastalon describing how it works, taken from this post and this post.:
Celatalon: The cap is 2x IP’s size at cast time. That cap takes into account all of the things that affect it.
Marokk: When you cast that 500K IP on top of the first one, I assume the cap is now 1000K? Also, what if you cast a third IP for another 300K absorb, is the cap 600K again? What happens to the extra absorb that's over the now 600K cap?
Celastalon: All correct. In the last case, the extra is removed.
Usually this won't affect how you play, but one implication is that you shouldn't use IP twice rapidly when you have a Dragon Scales proc active (which increases the value of your next IP by 60%). Your first IP will have a 60% bonus, but when you cast IP again, your total shield will be above your new cap and some of it will be removed. Here's a post from Ejs demonstrating how a lower 2nd IP can clip value from the first. Here are some numbers from a test Yse performed showing what happens, with annotation from me:
# IP without proc
1st 378,885 (this is Yse's base IP value. Cap = 2 * 378,885 = 757,771)
2nd 757,771 (the second shield adds to the first, creating a shield of 757,771. Cap is still 757,771, so nothing is lost)
# IP with proc
1st 454,622 (this value is 1.6 * 378,885. Cap = 2 * 454,622 = 909,244)
2nd 757,771 (the second shield adds to the first, creating a shield of 454,622 + 378,885 = 833,507. Cap is now 2 * 378,885 = 757,771, so 75,736 shield is lost)
If Yse has cast IP once, gotten a Dragon Scales proc, then cast it again, his shield would have been 378,885 + 454,622 = 833,507, which would have been well under the cap of 2 * 454,622 = 909,244.
Special thanks to Ejs, Yse, Beardyface, and L Kebess for digging through the details of this with me over the next few posts.