Awwwww yeahhhh...
Crabs were picked in FFXI because they were pretty harmless. No terrible AoEs, no huge single target TP moves. High defense, but easy to dispel. Anything else was a pain in the ass. Flies? AoE. Spiders? Sickle Slash. Crawlers? Slow. Vultures? Helldive. Goblins? Bombs. Beastmen? Variety of annoying shit. Manticores? Nope. List went on and on.
Don't forget Mandies with Dream Flower! And Colibris' TP erasure and stick-my-beak-down-your-throat-to-eat-your-food abilities.