the balances we need imo.
orisa, mei, hanzo and hammon is far the most out balances heros atm.
hanzo: arrow speed slowed down or projektil decrease
hammon: lower readius on the Piledriver and Adaptive Shield shuold not give shield if no heroes are near him
orisa: Halt no movment speed reducktion
sigma: dmg reduktion or a give him reload
mei: ulti radius reduced and walls hp is combained to XXX hp (not breaking tiny only a part of the wall)
genji: only resets dash when ulti is aktive
baptiste: reduce healing done and dmg done by alot but increase his rate of fire
bastion: reduce dmg on longer ranges
doomfist: reduce speed on rocket punch
phara: reduce dmg from rockets
diva: ulti bomb delay time increased or dmg reduced more for the distance of impakt
tracer: longer CD on recovering Blink
this is seen from a GM point of view. how much the balancing should be is blizzards job. if you want to know why the this is the balanace we need tell me what hero you want to talk about.