With unlimited instant logout, you could get your trusts back that died, or get full trusts. Slap a dot on the boss, log out instantly on the periphery of the battlefield, wait a few seconds to let the boss go back to the middle, log back in, get trusts with full HP and MP. Repeat as needed.
Anyhow, as others have already pointed out, this is easily fixed. Allow instantaneous logout if there is no enmity. Or even just in "safe" zones like cities. This would be a nice little time saver.
