yoshi has not been mastered, how many pro draconic reversers have you seen? if yoshi's dr was mastered he'd be a lot higher tier for having a wavedash. of course there's plenty of other yoshi technique's just like there is with everybody, but the dr is absurdly on it's own scale of dificulty and necesity in order to REALLY compete in metagame.
after him i'd say peach is dificult and then diddy kong
for easiest i'd say mk cus he really can mess up most heroes with just nado, up b, and dsmash
then DDD and snake cus when in doubt u cud just pull out a grenade