Why even buff marksmen in the first place
Seriously, when was the last time you were in game and thought "oh gee golly gosh, these ranged damage dealers are just so darn weak!"
No, in fact, I'm pretty sure it's the opposite and people actually are more likely to say "Yeah, range damage, fuckton of healing, self-peel and free true damage, REAL BALANCED." Yeah, that sounds much more likely. I get that you wanted adc variety, but I don't think each team picking 4 adcs and a support is the way to get "diversity"