Incorrect, Omega (and continuing to subscribe to such logic further proves, as each day passes, that you are Nebaris. You quoted him verbatim).
Not incorrect, no, and I thought you'd drop this whole trying to prove that I'm Nebaris mission you guys are on? Please don't go back on your word.
"The most powerful of these" refers to the Sith Lords of the Sith Order, descending from Darth Bane. To suggest that it refers only to Darth Sidious and Darth Maul requires a certain level of willful ignorance of the English language. If Sidious and Maul are the only Sith Lords being described, then they would have also spent the previous thousand years watching and waiting. This is a highly dubious contention.
Who are you quoting from? Whoever it is, s/he is wrong, and is the one being willfully ignorant of the English Language.
When the Sith finally emerged from a thousand years of watching and waiting, they numbered in accordance with the tradition set down by Darth Bane, only two.
There are two interpretations of what the "these" refers to.
1. This is essentially your approach, where you treat the "Sith" as the entire millennium old Order as what the "these" refers to, with the text that appears afterwards as simply describing into detail the current Sith, though not placing the focus onto them.
This is certainly a valid interpretation behind it, but not the only one.
2. This is essentially mine, where I'd conclude that the "these" refers to the then current two Sith Lords.
a) "When the Sith finally emerged" - quite clearly referring to Sidious and his apprentice, Maul.
b) "from a thousand years of watching and waiting" - not necessarily meaning that the emerged Sith themselves had been watching and waiting for thousands of years, but that they finally revealed themselves after such an amount of hiding and waiting had taken place, in this case clearly on part of the Ro2 Sith as a whole.
c) "they numbered in accordance with the tradition set down by Darth Bane, only two." - again, going back to describe the then current two Sith, rather than the entire Order as a whole.
Essentially, to interpret that the "these" might refer to the current two Sith is a valid approach, as long as the burden of proof isn't on me, which it isn't.
As for the rest, that's another topic in itself which I have no interest with arguing right now.
Prove it. His ability to manipulate others and his understanding of galactic politics is listed as "perhaps" his greatest weapon, and does not exclude his combat skills.
I probably should have elaborated more, but when I said that power, in this case, wasn't personal combat power, I meant that it wasn't solely personal combat prowess. I wasn't, and wouldn't deny that it was inclusive, on some level, of such power, given the quote makes a direct reference to his power in the darkside. But, it makes a bigger reference to his intellectual qualities, which would indicate that power, in this case, would include the non martial aspects as well.