Unless S-E did fix my problem, don't ever use <bt> with a range attack macro!!! It'll screw you over and make you look like a total noob!!!
What happens with <bt> is it locks with *a* battle target. And monsters that link are considered <bt> as much as the monster you're currently attacking. I sometimes got locked on a monster that had just linked, and I tried everything to get my target back on our current mob. I tried "change target", disengaging and re-engaging while targetting the mob in red... nothing ever worked!
The worst time it happened was while fighting the Bastok Dragon. It had just awakened and started striking our BLM. At that moment, my target switched onto the dragon, and I couldn't switch my target back to the Seeker. After that fight, I switched all my <bt> macros for <t>, and never had a problem ever again. I've made a second macro instead, which is simply "/target <bt>". I suppose there's an F* key that does just that, but I always had it easier hitting a macro than a F* key anyways.
I never heard any complaints about <bt> from mages, so it seems there aren't any problems with /ma commands. But for some reason, it did screw up my /ra. So do set your ranged attack macro to "/ra <t>". It will save you from looking like a total fool.