- Unit tracking via mouse over, target, party targets, death messages, name plate updates, and optional syncing between all teammates
Looking at that, the only way an alt will get the target in the proximo list immediately is on mouseover, target, death msg or having the nameplate visible when it updates. Also, if you mouseover them on your main but your alts get an event that pops one in first, I would think that would screw up the list order, making keybinds meaningless. The sync between teammates thing should do what you're after.