Our opponents were Kevin and Chad, both commanding hordes of Necrons. I'm not sure exactly how their points were split, but they had 4500 points between them. Having never played against Necrons, I had absolutely no clue what I was up against. I started getting worried during setup. (Please excuse the blurry pics. These were made with my cell phone.)
It didn't take long to tell that we were pretty much doomed. Tau need to keep decent range. Eldar need room to maneuver. With the board so packed full of infantry, neither of us had any room to play to our strengths. I was running two fire prisms, so I was hoping to even the odds a bit by clearing some room with large blasts. Unfortunately, before I got the chance to shoot, one went down to opposing fire. The other didn't manage to kill as many troops as I'd hoped.
I ran my seer council out front to throw some templates into the infantry and tie up some guys in close combat. Unfortunately, they ran up against a unit of guys that could ignore invulnerable saves. Needless to say, my council didn't last long.
We actually ended the game early because the store was closing, but it was quite clear who won. We got completely overrun by necrons.
I've learned my lesson... if the numbers go too high, politely decline to play. I'm all for playing big games, but huge point totals need huge playing surfaces. My bikes and skimmers need to fly around the board a bit, and an eight inch deep wave of infantry that stretches across the whole length of the table and advances each turn isn't really a fair fight for me. That many troops on such a small table just gave assault-oriented troops too much of an advantage... in the same way that deploying on the short table ends with no terrain in between would have given us an unfair advantage.
So far, this is the only loss I've experienced with my Eldar, and I'm going to count it as such. I guess I should have known better than to accept the game.