I don't think you get the concept of Tiered raid content. Eternity Vault and Karraga's Palace are Tier 1 Operations. Explosive Conflict is the first Tier 2 Operation. Storymode of EC is more difficult than EV and KP Storymodes, requires more gear, and drops better gear. It is intentionally not on the same Tier as EV and KP.
Just look at the drops:
Story Mode EV: Columi Tokens, Tionese Commendations.
Story Mode KP: Columi Tokens, Tionese Commendations.
Hard Mode EV: Rakata Tokens, Columi Commendations.
Hard Mode KP: Rakata Tokens, Columi Commendations.
Nightmare EV: Rakata Tokens, Columi Commendations.
Nightmare KP: Rakata Tokens, Black Hole Commendations.
Story Mode EC: Rakata Tokens, Black Hole Commendations.
Hard Mode EC: Campaign Tokens, Black Hole Commendations.
Now this is how I view how the progression is intentionally going(only the colors indicate the order):
Story Mode EV
Story Mode KP
Hard Mode EV
Hard Mode KP
Story Mode EC
Hard Mode EC
Whatever you feel I would say this is probably how they intend it. Due to what was said, look at the rewards. Nice observation.