As long as the buffing ensures it is equal to the difficulty of the original Kara, there should be no issues. If its over buffed like all the bosses/trash on Lordaeron, then yeah that sucks. Should be as Blizzlike as possible for the pure replication experience, seeing as Blizzard themselves refuse to launch Legacy servers
Even if it were fully pre-nerf with random annoying bouncing around, Maggy would drop like a sack because of better players, much more knowledge, better addons.
Once you kill all the channelers, he's pretty much a free kill. We were just talking and laughing on Discord today during p2 because that's how effortless it is if all the clickers know their job.