Black Arrow/Cold Arrow + Attack Detection Systems

I just noticed a problem im going to have, with giving Heroes abilities such as Black Arrow/Cold Arrow.

Basically these are spells which require the attack buff to remain on the target.
Attack Detection Systems, detect the damage then immedietly remove the buff, so that other damage sources dont get mixed up with attacks.

The only way i see is, to cast a slow everytime a guy is hit with Cold Arrow, and well Black Arrow will be alittle bit more tricky, but nonetheless possible.

Just checking to see if someone else has encoutered this problem and had an alternative solution?
Is there any 'clever' way to get around this?

thx

Nope, what you have there is your best choice, and it's not that bad.