A tiny number of players going out and playing rambo on the defense will drain their entire teams pool in about half the round. The ruins map for instance is basically the perfect defense at A but you still have people spawn at B. Because they respawn as quickly as they die, they're up to double digit death counts before the round is even halfway over. In my last game I spent 10 minutes waiting around at A twiddling my thumbs while the rambos depleted all the reinforcements. Then after all the reinforcements were gone, I got hit by a stray rifle bullet and was out of the game. It's a map that honestly should be impossible for the attackers to win on but I've never seen the defenders win on a reasonably full server.
I think the simple solution to this would be to put a 90 second timer in between spawns. So if you spawn and immediately charge the enemy to die within 10 seconds, you have to wait 80 more seconds before you do it again. That way if some people want to go play rambo, they will only be able to drain their team of 12 tickets over the course of the game. It could also create a way for the attackers to win without depleting the defenders reinforcements.
Edit: To clarify, I only want the spawn cooldown for defenders.