On the fitness side, it sounds like a threshold and VO2Max issue to me. Threshold will give you the ability to recover from earlier efforts faster, and VO2Max obviously helps with the digs too.

The thing to look out for though, is how much energy you're using during the race. Some races you just can't take it easy, but other times you should be able to come into the finale with NP way under threshold. Are there tactical decisions being made that are putting you in the wind to maintain position? Gaps in front of you? Cat 5 position (really high shoulders)? Too low of a cadence?