Target Marking bug

I play almost exclusively on controller, so instead of having the numbers 1-5 bound to actions on my crossbar, I've set a macro to cycle through the numbers for me. That macro is:

/mk attack <t>

With this command I can mark monsters with numbers in dungeons with a single button, instead of using five. The problem with using this command is that once an enemy is dead, the corresponding number can no longer be given to any enemy. If that enemy is alive, I can target it and use the macro which will remove the marking and I can reassign another enemy that same number. For example. In Amdapor Keep, I've marked a Dullahan as #1 with the macro. Using it again, I remove the #1 and then mark the Succubus as #1. However, if I mark the Dullahan as #1 and he is defeated, I can not mark anything else as #1. The next enemy, regardless if the Dullahan will be marked as #2 or higher. Once I've marked enemies 1-5 and they've been defearted, the command will no longer work.

The workaround for it is, I have to manually remark and unmark whatever numbers that were used for a slain enemy. So, if I've used all five numbered markers, I'd have to manually mark something, be it another enemy, myself, or a party member as 1-5 before the macro will work again, and before beginning my next pull. This takes a bit of time and frustrates other party members.

I'm not sure if this is really a bug, or an oversight. I've been trying to find a faster way to mark on controller since I've started tanking and I thought this macro would be the answer. There is even a similar macro that is set as a default macro that has the same problem. It seems like unless something is manually marked, or specifically marked as /mk attack1 <t>, /mk attack2 <t>, /mk attack3 <3>, ext, once the target is defeated, the markings never reset to be reused. It's as though that enemy is still there and marked, even though it's not.

To summarize:

1) Use command "/mk attack <t>" to mark enemy 1-5
2) defeat enemies marked 1-5
3) unable to re-mark enemies using the "/mk attack <t> command until I mark some 1-5 manually through the game menu or a marker bound to the hotbar or crossbar and remove markings.