Even assuming ZOS RNG was working in precisely equal measure, with no hidden bias towards certain sets or traits, nothing OP said suggests there is some lower rng for infused netch pants.
Not 100% certain, but I believe there are at least 3, perhaps 4 sets, that drop in that dungeon. Each item of each set can come in one of 8 traits.
For just 1 set, that is 7 pieces x 8 traits or a 1:56 chance you will get the piece and trait desired. Now add the loot table where a drop doesn't always mean a netch set piece, but could be one of 3-4 different sets.
You now have a 1:168 chance with 3 sets in loot table, or 1:224 with 4 sets.
If you want divine or infused netch pants, that means 1:84 or 1:112
Let's say for sake of ease there are only 3 sets in that dungeon, that's still 84 drops of set pieces before you can even say you have worse luck than expected.
How many set pieces do you get in an avg run? 5-6 at most? Usually less but say 5 for easy math - that's still 17 runs of the dungeon before you even say your luck is worse than expected. You could get lucky and get it on first run, but even if ZOS RNG were not secretly weighted to limit the better drops like divine or infused, you're still looking at a LOT of dungeon completions before you can say divine/infused is not dropping for you in any given piece.