Let me tell you from my latest SP game:
Mictlan managed to kill itself off very early. Must have been the combination of dormant pretender, relativly low starting dominion and some really bad luck in combat (losts its prophet when taking the 1st indy province), and maybe even the loss of the starting temple from random event (Yes, this could happen to a player with a 'risky' setup as well
).
I didn't border Mictlan directly - there was a 'untakeable' indie between us right next to my starting province, and some impassable mountain borders, and 3 more indies. But when I sneaked an amphibious force along the cost to take the undefended provinces, neighbouring Pangaea immediately declared war on me. Most interesting: it was still 1 indy province away from bordering me directly, and took that province on the next turn, and send some forces into Mictlan territory. I barely managed to reach Mictlans home province before Pan did, and now I'm in deep trouble to fight him off.