@TheOne:
Fallen Down is like an energy beam. Doesn't have to be an explosion to do damage to the enviroment. It's damage output was so low it couldn't vaporize tree trunks in the entirety of the area affected. So, even the damage output is very low. Ainz says the spell is good against undead, so that's prob why he used, but this still shows that it's damage output is way lower than the potency of Creation.
You fail to explain why a non-combat spell would be necessarily weaker than combat ones, when literally everything points to the contrary.
The number of Magic Arrows per cast seems to vary. A random adventurer had 2, Iguva had 3, Ainz likely has more, and that's without tripling or dubling it. Ainz upgraded it to the 10th tier, so the number of arrows got likely even bigger. He mentions thirty per cast:
"In accordance with Ainz's command, the [Triplet Magic Greater Magic Seal] triggered three magic circles, each of which released 30 streaks of light, for a total of 90."
He tripled it, then he got ninety arrows in total. He clearly means that each cast of the Magic Arrow spell was upgraded to the 10th tier. Three 10th tier spells, the only logical explanation, unless you actually believe that Shalltear would survive ninety 10th tier spells. Imagine ninety lvl 100 magic casters launching 10th tier spells at her, you think she'd shrug it off like that?