[Brainn]

do your unitframes use a border by default ?
you could use the 'Backdrop Border: Colorizer' feature to use it as a debuff indicator (thats what i did in my raidframes).
you create a 'Color Conditional' variable that changes depending on a 'Unit In Set' variable, then use the Backdrop Border Colorizer to apply that color to the unitframes border.

do you use some of the downloadable ui packages or a full custom ui ?
its a bit difficult to guess how the unitframe you are trying to change is working, if it is a custom created unitframe/design a backup file would help to understand how it works.

/edit
found your recovery file in your other post, i think you are talking about the Raid_Main_ds file ?
what i did in my raidframe was using multiple conditional color variables to produce a 'priority coloring' of the border (@magic [blue] > @disease [green] > hasaggro [red] > 'nothing' [white])
thats like 3 conditional colors:
conditional1: @magic, true = blue, false = conditional2
conditional2: @disease, true = green, false = conditional3
conditional3: hasaggro, true = red, false = white

you could create a secondary border and use that for debuffs only and hide it if no debuffs, so you could see the aggro and debuff indicators at the same time.