Awww, I get to be part of a legend, and then it's like that
Oftentimes it's more cost-efficient to outpreach a single or even a couple fortresses in my experience as well, and it's not that uncommon in MP either. What is more difficult is dominion-killing someone who still has a significant amount of land. While undoubtedly possible, I suspect it's rarely worth the trouble, since usually everybody uses a reasonably high-dominion pretender (which translates to efficient temples and high concentrations of dominion) or else has a special plan to avoid dominion death.