Please do yourself a favor and listen to what they're saying now, rather than later. Use a damage detection system. People didn't code that for the luls, they coded it because WC3 has no good way of detecting and editing damage without a pretty complex system running under it. The "Attacks a unit" event doesn't work. It gets called when the attack starts not when it hits, which can be pretty far apart, especially for ranged heroes. And it cannot detect damage dealt or edit damage dealt.
This isn't overcomplicating it, it's just using the proper tool for the job.
With a damage detection system, this is 3 lines of code, even in GUI. Without a damage detection system, you might be able to hack together some terrible code to do this and it will look and perform bad, and it will probably take you 10x the time. We say to use a DDS because lots of us have tried to do this kind of thing without DDS and failed it.
The awful non-DDS way to do this would be to detect an attack and add Critical strike if the unit has the buff, or remove it if the enemy doesn't (don't do this).