I was not aware that there are actually three different groups of soldiers defending ancient sanctuaries until I was constantly attacking them during the race against time event to look for soul splinters. Some attacks resulted in low casualties while a few others caused high troop loss eventhough I sent elite troops in really large number. Some times later, my blog got a sanctuary strength search hit, it then occured to me that these sanctuaries might have different types of soldiers in them. So I took a closer look after each attack and found out that there are indeed different defenders there.
So this was my findings. The first two defenders could be vanquished by sending some 60k royal knights, 120k battle mages, 90k battering rams and 100k of other soldier types. The one swarming with corrosive worms, if you want to abolish them, need like 200k batering rams, 80k royal knights, 150k battle mages and 150k other soldier type, but still casualties and deaths are massive comparedbto the other two. (Just noting that my city is equipped with one 5 star level 8 attack rune and one 4 star level 7 attack rune).
The problem with sanctuaries is you cannot collect intel. You just attack, fingers crossed! Anywqy, happy sanctuaries attacking all!