QUOTE(folwaR...)

What is the optimal end game build for 1H heavy? I propose this:
For Arenas (SG) use ethereal rapier of slaughter, IW10 to Butcher 5, Fatality 4 and dark/holy strike, for everything else (non-SG monsters) ethereal shortsword of slaughter with IW10 Butcher 5, Fatality 4 and cold strike (to sync with flame spikes). Other equips being savage ... of slaughter with IW10 to Juggernaut 5 and then anything else (shouldn't be Capacitor too often). For shield it is force shiled of protection/warding with SDE.
In isekai, the end-game build of 1H would be ethereal and with fully forged agility, in my opinion. I am not so sure about persistent.
If the Tower came over to persistent one day (as was originally rumored to happen, replacing the Item World scaling) then persistent users might want 2 end-game rapiers, or 3 end-game rapiers if you consider SG and non-SG to have a different best one. In practicality very few users could afford that, so you'd choose 1 end-game fully forged rapier (thus ethereal with fully forged agility).
Savage of Slaughter is too expensive with relatively little offensive benefit to savage and a possibly non-meaningless sacrifice in defense, so unless you are the super-duper perfect peerless 1H warrior, I don't think anyone would recommend going pure Savage of Slaughter. Maybe one or two pieces at most. Don't sacrifice good Slaughter adb rolls for Savage (only sacrifice your wallet).
(It would still be interesting if you could be pure Legendary Savage of Slaughter with good adb rolls, though I wouldn't aim for it, so usually people start transitioning to Peerless Color before they could get all Legendary Savage of Slaughter at non-ridiculous price).
If you think you can keep Agility at zero then you shouldn't forge Agility. In practice it seems that most 1H users don't want Agility at zero, just varying levels of lower. In this case you can forge Agility, though it would still not be worth the cost unless you have lots of credits. I'm not sure what the answer is, and would be interesting to see more discussion on that myself.
I don't know why Noni recommended a Tempestuous Shortsword. But assuming you believe in the Shortsword (which evidence generally points to as correct for endgame) then you need to be using Full Imperil style. In this style, it is arguable whether Elemental or Holy/Dark prefix is better for SG levels, I've always thought it depends how you play (skill usage versus beatdown on SGs). Consensus seems to be that Holy/Dark is better for SG levels. A proper analysis would consider which arenas you do: a truly rigorous study has not been done.
Don't forget about your infusion element, by the way. You should be switching your infused element according to the day and changing your spike shield to match one of your elements, in my opinion. Even if you do this, as noted it's still better to have the best element be on your weapon. It's generally said to be Arctic (especially if you think the counter attacks loss from non-Fire shields is an overriding factor, which was originally thought but I argued against that years ago). Tempestuous is the next inherently strongest element, and actually the elements vary based on the current monster population, so Tempestuous could be the strongest these days, I have no idea.