“How many Scuttle Crabs would the Rift ecosystem in theory be able to support?”
I had always assumed she was a scavenger, because her claws aren’t great for fighting and she kind of has an isopod look, and they tend to be scavengers (or really icky parasites, but we won’t go there).
The biomass of scavengers that an ecosystem can support varies a lot. For example, the deep ocean has a lot of animals that scavenge because there is no real plant life to support the herbivores that are low on the food chain of more familiar ecosystems. When something giant like a whale dies, there can be a feeding bonanza, but those animals may not eat again for a long time. Fortunately, cold-blooded animals can often go a really long time without food.
That said, the Rift Scuttler is freaking enormous, so we’re not talking about swarms of flies or ants descending on a carcass.
On the other hand, dead animals is something the Rift ecosystem offers up really frequently. Raptors and dragons are dying constantly, and champions are dead on the battlefield all the time. So there is a lot of carrion out there.
Large scavengers in the real world, like vultures, tend to cover a lot of area, much larger than the Rift (or at least the portion we play on). On the other hand, mortality of Scuttlers is also really high so their competition with other Scuttlers for resources is probably low. Their population is a bathtub that never fills up.