His death was was brought up multiple times though. Have you completely missed the plotlines of Gaku'ei and Kinmou attempting to avenge his death?
Also, I don't the Keisha was 'the 3rd or 4th strongest' in Zhao, even at the time of his death. There was a fairly large pool of powerful GG-calibre commanders who, although their allegiance to Zhao was a bit complicated, should have scaled higher than him (Kouchou, Rozo, SBS, Chou Kotsu (?) etc.).