Yes, 1 point of suppression + 1% spell hit is enough for pvp cap.
The build that you linked is actually terrible, as I said before, you need to do damage. I'll be using something like this:
http://calculators.iradei.eu/talents...00000000000000
You can swap imp curse of weaknes for 5/5 suppression, the reason for this as you mentioned, rogues have additional spell hit penalty with talent, and additional spell hit penetrates cloak of shadow, meaning you will have more chances to dot into cloak, that is crucial against 2dps with rogue for example.
You need nighfall as well as other +dps talent from affliction. From that build you can swap 2 points of demonic resilince into affliction shadow mastery, if you can survive and you have no trouble healing pet.
Dots are binary spells, meaning they only can hit or resist, resistance dont decrease damage but increase chances of resisting that spell. Formula is simple, (Resistance/350)*0.75, meaning if enemy has 70 resistance he will have around ~15% to resist any binary spell (dots, fear, curses). By having 1 spell penetration you decreasing resistance of enemy by 1.