[Shujin]

Yeah it's slightly higher but Astralbelt has also some mean damage potential with magnetize. Also just make darkshield stealable if thats the issue
or 1 res per 6 instead of 5 void energy.*shrugs*

if I compare the 3 skills I come to the following if narrowed down to what they do

Astralbelt: 8 Rounds 10Def(12 with spirit), can be used on others, twice def bonus damage if pulled(can be combo into multipulls perround),Out of comabt persistence(saves you the set up), can be autoenchanted(also set up saving or with the persistence over battles you can put on a galren as auto echant, outclassing the boost darkshield gives easily). Can be stolen though

Ice point Guard: 8rounds 5 Def/Res(6 Def/res with spirit), Grants the abillity to guard which is veeeeeeery good, Can be used for an snipe attack, persists after battle saving you the set up of 6M. Can't be stolen

Darkshield: 8rounds 13res(no real benefit for spirit except for 3% dark resist as passive) consumes your void veil completely (or half now in turn for some damage), Has the passive effect I guess, does not persist through battle. Can't be stolen.

So compared to the other I still believe they are very much the same tier of skill, and void assassins that are focused on more melee void stuff, recover void energy a lot slower, So the viod costs are alot for them. (Like the VAs that actually don't use revile fray so they can set up melee attacks easier) So to be honest? I do not see a big issue for it to do the same as the other two skills of the same skill tier. Its not really better than them, it's just slightly different. and at full potential it just has 1 single stat point more, which doesn't meann all that much in diminishing returns, even without nerfing darkshield.
In the end I am indifferent towards it, it just felt off and I mostly suggested that for concistency reasons and easier dungeoning