We all would like to see more in the arena. In the end though, with lower numbers, how many can you fight at once? Using numbers as an excuse is just that... an excuse. 500, 300, 150, just an excuse for the real reason a person is not playing.
I posted earlier about many of the reasons I left the game. This time I'll relate a short story that could easily have been added to that list.
I logged on one night, I believe it was about 1:00 AM Central (not exactly prime time) to the old pinwheel map (forget the actual name). None of our bases had been captured so no matter what I was going to have to fly across a channel (2-3 sectors) to find a fight. All the dar bars indicated likely single opponents across the channels. So I upped and headed toward one of those dar bars. Just as I was about to get there the dar bar disappeared and the next closest one was three sectors away. My choice at this point was to fly home, bail or fly toward the next dar bar. I always flew to kill or be killed so I headed toward the next dar bar. It too disappeared by the time I got there. Finally, after flying two sectors back in the direction I had just come from, I got to engage a bomber. This was a 9-10 sector flight to get one kill and land.
Numbers do matter. Spending 20, 30 or 40 minutes simply looking for someone to engage isn't really much fun. And to answer your earlier question, 4. That's how many I've survived against (on multiple occasions) fighting them all at once on my own. Five is too many.