As diana, Proper warding from the enemy team can diminish Diana’s flanking potential in team fights as she will be detected by the enemy in time. This can really reduce her ability to team fight.

When ganking an enemy, if she misses her Q, her gank will most likely fail as she will be unable to use her t twice. She will also miss out on a lot of extra damage.

Unfortunately, Diana relies on getting ahead. If you do not get ahead on her, the likely hood is that you won’t be strong in the later parts of the game. As diana, A good guard of the enemy team can reduce Diana's flank potential in team fighting as it will be detected by the enemy over time. This can really reduce her team fighting ability. When she spoils an enemy, if she misses her Q, her gank will probably fail because she will be unable to use her t twice. She will also miss a lot of additional damage. Unfortunately, Diana is counting on moving forward. If you don't advance it, the likely hood is that you won't be strong in the later parts of the game.