as much as i enjoy mirror and limited 1v1 arcade, a few heroes stand out as making the matchup or mirror matchup boring.
orisa- basically just shoot at the sheild and wait to get close to attack or become friends with the enemy
sombra- invis the whole game until capture point unlocks
moira- SUCC and hope they cant track- the opponent and i got our ults 3 times each before we drew 
i would suggest taking them out of the rotation and putting characters like rein, hog, dva, bastion, torb. (i think i missed some and some are already included but i hope i got my point across) 