Oof. Seems like no one knows what exactly the issue with SKS is.
I wish I had one of my twitch clips explaining the issues with MCH that have been around since 4.X and why Skillspeed is the worst stat for any job in this game. Probably even worse than Piety on for Paladin.
The Machinist rotation's goal is to use Wildfire at exactly 60 seconds to line up with Trick Attack and other Party buffs. Take for example O6S (Sigma V2S) where you have 100% uptime. Depending on your SKS/Rotation you delay wildfire every time by 1-2 seconds, drifting further and further until you miss trick attack completely. Last tier we had a BiS GCD speed of 2.48 - a rotation called 65H ended up with a small amount of waiting after the last GCD to line up wildfire perfectly every rotation. Let's call those "Perfect rotation time". Now if you add one GCD to your rotation and end up at 70H you need a GCD speed of around 2.40 - 2.41 for this to be the "perfect rotation time". Yet, being at 2.40-2.41 GCD speed comes with other problems.
One of those is obviously Clipping. You will clip most OGCDs with that amount of skillspeed, not to mention Double Weaving. Your Reload outside of Wildfire needs to be either delayed or you clip your GCD. You'll also clip with Turret resummon after blowing him up and using QR there. Other noticeable clipping was for example dismantling First forsaken in o8s.
SKS's value besides buffing Auto attacks is close to 0. It can help with getting that last GCD into overheat window but I manage to do that on 2.50 GCD speed too.
To sum up : SKS will make you clip, not kill your rotation but just make you lose DPS overall instead of gaining DPS. We don't gain damage from DOTs neither, since we don't have any.
To give examples on how far we go with this is:
1) This tier Crafted Ring Pentamelded is better than the Savage Ring.
2) Last tier Pentamleded Belt was better than both 370 Belts.
3) Deltascape the 24 Man Headpiece was better than both 340 pieces.
This is all due to Skillspeed having no value at all for Machinist.
So yes, putting SKS onto the Raid weapon is bad, it's really bad. Calculations I made show that the difference inbetween the Raid weapon and Tome weapon are around 0.6% (with rotations kept in mind) with tome weapon being nearly as strong as the raid weapon this tier around. This has not happened since Creator. It is always supposed to be Raid wep>Tome weapon. There's basically no reward in clearing O12S for Machinist players this time around. Everyone is already talking about the Eureka Weapon probably being the best before Echo is even around.
The above linked Ariyala link is also wrong. I found out yesterday that the Crafted Ring is better.
I'm not very big on Math, I use provided Calculators by Lynn Nuvestrahl in the balance discord but go a lot myself by feelycraft. I've been playing MCH since 4.X and have cleared everything but Ucob (cleared on SMN) on Machinist. Currently in o11s progression.
I am probably part of the people that play Machinist the most worldwide and I have very good understanding of how the class plays and what's optimal on it.
Giving us SKS on the Raid Weapon was another bullet to the knee considering Bard is already the much stronger counterpart.