In short, the point of this post is to point out the 5-piece bonus of Mother' Sorrow is underperforming as of patch 3.1.0 because of the buffs to 2-4-piece bonuses on Spell Critical and Precise Weapons.
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With the latest PTS patch notes it appears to me that the developers are trying to renew the balance between Spell/ Weapon Critical/ Damage/ Penetration and Max Stamina/ Magicka and also standardize the Mundus' and Traits' effects; for example,
Raw Resistances provided by the Lady = Resistances provided by a Defending Weapon,
Raw Penetrations provided by the Lover = Penetration provided by a Sharpened Weapon,
Raw Critical Ratings provided by the Thief = Critical Ratings provided by a Precise Weapon
and
Raw Spell/ Weapon Damage provided by the Apprentice/ Warrior = 238 ~= 235.65 = Spell/ Weapon Damage provided by a Nirnhoned Battle Axe/ Greatsword/ Maul
(note that Staves, Bows and 1H Weapons gain less Spell and Weapon Damages from Nirnhoned because of their lower Damages).
However, the 5-piece bonus to Mother's Sorrow and Spinner looks very odd to me -- currently, at patch 3.1.0, the standard Critical Ratings granted by a 2 - 4-piece bonus is 1066 while the standard Penetration granted by the same bonuses is 1487. If we compare their 5pc bonuses to the standard 2-4pc bonuses,
Mother's Sorrow 5pc = 1643 Spell Critical = ~1.54*standard Spell Critical bonus
and
Spinner 5pc = 4000 Spell Penetration = ~2.690*standard Spell Penetration bonus.
If we look at the old values, the standard Critical Ratings granted by a 2 - 4-piece bonus was 688 while the standard Penetration granted by the same bonuses is 1935; therefore,
Mother's Sorrow 5pc = 1643 Spell Critical = ~2.39*old standard Spell Critical bonus
and
Spinner 5pc = 4000 Spell Penetration = ~2.07*old standard Spell Penetration bonus.
To help understanding the change in ratio of 2-4pc bonus to 5pc, here are some numbers for reference:
Hunding's/ Julianos = 299 Weapon/ Spell Damage = ~2.32*standard Weapon/ Spell Damage,
Draugr Hulk = 2500 Max Stamina = ~2.28*new or ~2.59*old standard Max Stamina.
As a summary, if we compare some (only bonuses which provide unconditional stats, so sets like Scathing are not in these calculations) 5pc bonuses to Weapon Traits, Mundus Stone Effects and 2-4pc bonuses, we have
Spinner 5pc = ~1.45*Sharpened Weapon = ~1.45*Raw Lover = ~2.690*Spell Penetration bonus,
Mother's Sorrow 5pc = ~0.833*Precise Weapon = ~0.833*Raw Thief# = ~1.54*Spell Critical bonus,
Julianos 5pc = 1.495*Nirnhoned Staves## = ~1.26*Raw Apprentice = ~2.32*Spell Damage bonus,
Draugar Hulk = 1.23*Raw Tower = ~2.28*Max Stamina bonus.
#
2191 Spell Critical = 10% Critical Chance at CP160
##
New Nirnhoned = 200 extra Spell Damage at CP160 on Gold Staves unbuffed
Upon consideration of the above values, I believe it is fairly obvious that the developers overlooked some 5pc bonuses because it is makes little sense how Mother's Sorrow 5pc provides less Spell Critical than a Precise Staff while Spinner grants more Spell Penetration than a Sharpened Staff and Julianos gives more Spell Damage than a Nirnhoned Staff. A 5pc bonus simply, in my opinion, should not have lesser effect than a weapon trait.
If anyone has anything I missed, noticed anything I am wrong or think if there is anything I should add please let me know. Thank you very much for reading.
@ZOS_GinaBruno could you please kindly pass this to the team and confirm if not changing Mother's Sorrow 5pc bonus while changing the 2-4pc Spell Critical bonuses and the Precise trait is intended or not? Could you ask them if they are going to review sets with 5pc bonuses related to Max Stats and Criticals in the later patches also? Because, for example, Destruction Mastery is also in a horrible position as well considering Destruction Mastery 5pc = ~2.19*Max Magicka bonus = ~1.18*Raw Mage even with the extra requirement of having a destruction staff equipped. Thank you very much for your help in advance.