So, I won my first non-SR victory on BtS today, diplo, Alex, Noble, Pangaea, Epic, Lrage, but only cause I had so many vassals. Can any of you guys win a diplo victory with no vassals at all?

I just did a AP coup. Surprised the heck out of me, but got 55K score on noble for making Augustus feel special at around 1000 AD, and didn't even build the AP myself. I won the first election, and the first vote I put was Diplo victory as Egypt (Ramses), and amazingly got it passed.
Caveat was the game was Panagea, normal, small (not standard).

Early warring with the war chariots (didn't even wait for a barracks), horses at the capitol, and kept number of angry opponents to a minimum was main pathway to success. Rarely razed and rarely founded my own cities, except away from the enemy. Neglected teching once had iron+animal hus, and was at zero research, with slight negative balance, due to always expanding (thanks to captured barbs). Key diplo with Augustus was to switch to his religion when he asked, not to crowd him, and a mixture of resource gifts and tech trades. And of course had the biggest most populous empire, so my vote was the bulk of winning the vote, though not 100%.

It's nice to know that an AP coup against the AI is possible, just like they can pull against the player.

My highest scores have always been diplomatic wins, but that was on vanilla. So far I've only gotten cultural and space race on BTS

I consider diplo to be one of the easiest ways to win...I am finally trying to win a military win buts its a huge earth map so I am not sure if I will be able to manage to do it in time.

Well I got an Augustus level socre for this 25000 I think. Kind of stupid when I wouldnt have got anywhere near that high a score if I had turned diplo off and subsequently conquered the rest of ther world