Yes, there is only one level to Yamotsu Mines and, yes, the fire beetle spawns only at the very end of the Mines. There is no recall or marking inside the Mines.
I tend to take a mage/tamer down there and simply run past the spawn - invis to break aggro as necessary. Since there is seldom anyone up that end, it's not usually a problem to move the surrounding spawn a little south which has the effect of clearing a taming area so it's just me one on one with the fire beetle. I cast one e.v. to subjugate the beetle and immediately pre-cast mass dispel so my e.v. doesn't inadvertently kill it. I dispel my e.v. on receiving the "subjugation" message and lead tame as usual.
If I am particularly unlucky and I fail often enough to need to subjugate the beetle again, I simply ping it with magic arrow spells to subjugation point again, and recommence lead taming. Mount up and ride it out of the Mines, running past all spawn again and invising where needed to break aggro.
It's really no biggie if you do accidentally kill the fire beetle while perfecting your e.v./subjugation technique since there is there is no significant delay in respawn, and it only ever spawns in that immediate area.
If you're on Europa, I'll gladly show you.
Good luck & good hunting!
