[DonCorazon]

Diplomacy is the most directly correlated to how long you can survive in an MP game. It fades in importance as the number of players decrease. In the end, even the smoothest diplomat will still need to face at least one enemy to win, and that is when you need the deep knowledge of the game.

I survived many MP games and did well on all the graphs based on diplomacy but in the end would get slaughtered (see Endgame Slaughter Moves thread) because of lack of knowledge of these endgame tactics (or in that case, it turned out to be a bug exploit).

Now I understand many endgame strategies but still am learning specific tactics - spell combos that are effective, units to deal with specific situations, etc.

So I think there is a learning curve you need to move up and the important skills shift throughout the game, but diplomacy is the most important until the very end when your ability to handle endgame clashes will determine whether you can win or not. Of course, you will never get to that point without some diplomatic success.