So while I was writing this I found how Needle Blow and WugongGu scales with the help of a Wugushi3 friend and my own Wugushi2.
Anyways this was done with various physical attack ranges and attribute levels tested on 4 different mobs - Hallowventer (Fedimian Suburbs), Red Socket (Sentry Bailey), Blue Ticen (Sentry Bailey) and Blue Socket Archer (Sentry Bailey). Needle Blow and WugongGu both tick for the same damage on all 4 mobs.
The testing was done with no weapons at all until the end and each testing phase consisted of using various equipment that increases both minimum and maximum in order to remove variance from the poison tick damages.
https://imgur.com/Gxgi280
My findings is that regardless of attack range (at 727 and 1022) both skills scale at a flat rate with attribute levels and also seems to scale 1:1 with physical attack which is also unaffected by attribute levels. What I did find interesting was that the supposedly flat increase for Needle Blow at Lv20 increased by 7 damage at 21 but 8 damage at 22 and 23 which means it may in fact not be exact flat increments but may have something to do with the skill damages. At Lv10 Needle Blow skill damage is 776 in which 1% of that would amount to 7.76 damage.
.2 x 776 = 155.2
.21 x 776 = 172.96
At this gap it didn’t break the whole number and ToS rounds down resulting in the +7 gained from attribute only.
If this is true then it should repeat itself again at Lv26 when it’ll increase by 7 damage yet again because of not breaking the whole number in order to gain 8 damage and again at Lv30.
.25 x 776 = 194
.26 x 775 = 201.76
My results
Lv25 = 1429
Lv26 = 1436
Another difference of 7.
Lv29 = 1459
Lv30 = 1466
If this is true then for WugongGu, its skill damage, 1102 at Lv10 would mean 1% of it amounts to 11 damage added to the poison tick per attribute level which correlates to the 11 damage increase per attribute level as seen on the table.
In order to confirm my theory I needed a Wugushi 3 to confirm me his Needle Blow scaling. Lv15 Needle Blow has 1050 skill damage and Lv15 WugongGu has 1547 skill damage. To stay relevant each attribute increase should increase the damage accordingly - 10.5 damage per Needle Blow and 15.47 per WugongGu.
Needle Blow
Lv60 attribute - 2226
Lv61 attribute - 2236
tl;dr
Wugushi skills scales based on physical attack to poison damage per tick at a 1:1 ratio and attributes scales at 1% of the base skill damage. This means that if you don’t go Wugushi3 your poison damage aren’t going to scale as well. While you are a Wugushi2 you’ll only gain 7.76 per Needle Blow and 11.02 per WugongGu while a Wugushi3 will gain 10.5 per Needle Blow and 15.47 per WugongGu on top of having a longer duration for more uptime.