Elidibus was the most powerful ascian, he was selected the Heart of Zodiark for a reason.
-He released himself from a binding spell from Hesperos and Lahabrea very easly while Emet-Selch struggled with someone like Hermes, which is less powerful than Lahabrea himself.
-He could manipulate light and dark magics easly.
-He defeated the WoL twice, one on Ghimlyt Dark and the other one in The Seat of Sacrifice, the WoL was defeated but saved by Estinien and Emet-Slech/Graha'Tia respectively.