User blog comment:Hermione Chase/"The Blood of Olympus" Expectations/@comment-4902593-20140111151738/@comment-5927468-20140111220454

It's not about them being the most powerful. They each play a unique role in defeating the giants and Gaea. It just isn't entirely clear what some of their roles entail.

Annabeth acquired the Athena Parthenos and was able to contact Reyna so she could deliver it to CHB. This will presumably ensure that the camp war is averted and the gods will be healed of their split personalities. Then all the gods and campers can join in the fight against the giants. She also convinced Damasen to help unchain the doors of death in Tartarus.

Hazel has become the team's magic expert, which came in quite handy in HoH and may continue to do so in BoO. She also killed Alcyoneus in SoN.

Leo built the Argo II, making it a lot easier to travel across the Atlantic. There may be more for him to do in BoO

Percy and Jason are the champions of their respective camps, so they were the best candidates to try create a level of trust between the two, with some success. They're also both quite skilled in combat.

Frank freed Thanatos in SoN and became an outstanding soldier and leader in HoH. This is bound to be important later on.

Piper freed Hera in TLO. Other than that, I agree that her usefulness has been limited to using her charmspeak and knowledge of old stories. I suspect she's going to play a bigger role in BoO