I take it some shrines are invulnerable? Cause I found a shrine of a god I really don't like too much, and used two full loads of gorgogs, 50 of them, plus the whole presidio of the damned worth of critters and it still hasn't fallen... I'm getting quite peeved.. Is it possible this particular shrine is invulnerable?

Only the fulcrux shrines are invulnerable.

a fully sanctified shrine with all rooms fully sanctified takes about 870000 essence to take down (probably more), that is one fully imbued item a room, what you offered does not even come close to that

One room takes a bit over 65k essence. I think it worked out to be around 80 Astral creatures. So like Anisu said, you are nowhere near what it takes for even ONE room.

Actually, 50 gorgogs, seven brains, and 12 aberrants (assuming those are the correct quantities) adds up to 60548 essence.

Hrm, I had been told gorgogs were a bit less than astrals. I really need to get a list of essence per corpses

Astral respawns range from 555-1146 essence, depending on the astrosphere. Linked astral creatures usually are worth between 1000-3000 essence, with a few exceptions. Linked mobs have no set amount - their essence value fluctuates with their health/damage.