I've tabbed that whole song but have no way of sending except a old guitar pro
The fills on Cast Down The Heretic are generally quite simple, here's a few techniques George uses quite commonly not just from Cast Down:
ride bells beore a fill such as (X being the bell hit):
Code:
C--------------------------x---x-------------------------x-
R-x---x---x---x---X----------------------------------------
t-----------------------------------------x-x-x-x----------
T------------------------------------------------x-x-x-x---
S---x---x---x---x-----x-----------x-x-x-x------------------
B-x---x---x---x---x-------x-x-x-x-x-------x------x-------x-
Cymbal accent patterns such as in Execration Text:
Code:
C-x-----------x-----------x-------
S---x-x-x-x-x---x-x-x-x-x---x-x-x-
B-x-----------x-----------x-------
splitting solid 16ths between bass and snare with cymbals:
Code:
C-x---x------------x---x-----------
S---------x-x-x-x----------x-x-x-x-
B-x-x-x-x----------x-x-x-x---------
Enjoy

It all changes live though, most feels are improv except where the fill is linked to the riff for example the huge fill on the end of Execration Text.