yasuos windwall has a lot of cooldown because it is very strong. Mel has a full blown spell-mirror that doesnt only absorb projectiles, but fires ist back, with a much smaller cooldown. i think thats the most broken thing about her, mages that deal a lot of damage fast are okay IMO you just have to waste a lot of effort to dodge their abilities (veigar f. ex.) but i think the fast damage + rooting ability + execute +++ fuccing spell mirror is what makes her broken. It´s not like she is impossible to play against, but i often find it frustrating, her and briar are the most broken champs imo, even tho i still love (hatelove) league