The attack damage % used by Resonating Shield is derived explicitly from the base off hand physical damage inherent to the gem itself. No amount of damage on a weapon in the main hand will contribute to Resonating Shield damage.
Focusing on the Armour value on your shield is one of the methods for scaling Resonating Shield damage.
Passive tree nodes that contain the text X% increased Defences from Equipped Shield such as Towering Shield, Core of the Guardian, Spiked Shield, and Flashy Deflection do not impact Resonating Shield damage. Instead, they impact the final Armour value added to the player rather than the implicit Armour value of the shield itself.
Gem level progression
Level
Mana Cost
Attack Damage
1
0
0
417
30%
2
3
9
482
33%
3
6
14
552
36%
4
10
21
627
40%
5
14
28
708
43%
6
18
35
794
46%
7
22
41
886
49%
8
26
48
984
52%
9
31
57
1090
55%
10
36
65
1202
57%
11
41
74
1321
60%
12
46
82
1449
63%
13
52
92
1585
66%
14
58
103
1730
70%
15
64
113
1885
73%
16
66
116
2049
77%
17
72
126
2223
81%
18
78
137
2409
85%
19
84
147
2607
89%
20
90
157
2816
94%
Recommended support gems
The following support gems are recommendations by GGG as listed in-game, and do not necessarily reflect optimal combinations or the views of the wiki.
Gem tier
Support gems
I
II
III
IV
V
Item acquisition
Resonating Shield has restrictions on where or how it can drop.
