the best way to balance marksmen is to actually fucking balance marksmen.
people tend to forget, that theyre not the only type of carry in this game, but the only type of carry that is massively overtuned with the additional support protection.
if supports were the problem, then melee adc, apc, skirmishers and juggernauts would take over games the same way marksmen do with the additional support shielding and cc. but they arent. marksmen scaling is overtuned, and thats why.
they hit their power spikes off 2 zeal items and i.e. because zeal items have been made cheaper and more powerful.
theyre not overtuned because of enchanters, but because of direct buffs to marksmen and their itemization, and direct nerfs to marksmen counters like assassins and burst damage in general.