I'd say the Freaks poison is still less threatening. It pretty much takes one Sob to stall the poison enough to still have a fighting chance, barring the occasional Bogdan/Shazam. Whereas Greem needs to be taken down, and she's somewhat useful even at the third round given the damage potential and low minimum.
The main reason to ban grudg,which I can think of,is to give chance to another underrated 4* . Have a look madelona,Wolfgang,Pyro . No one using them but Bogdan,grudg in split decks. When do you see those cards used? When the player is poor not to afford Bogdan . Banning grudg will give greater chance to them,and they are really good if given the chance.
But ,unbanning Olga at the same time doesn't seems fair,does it? Even if someone wants to fill the grudg spot,he will replace Olga their and save an extra star . So,4* characters other than Bogdan,grudg will still go underrated and unused.
Now when Grudj was unbanned,most famous split deck -> 4/4/2/2 or 4/4/3/2
But now with Olga,the decks will get more stronger and OP ->4/3/2/2 or 4/3/3/2 ,thus allowing the other half to get more stronger .
In all,I would appeal to keep Olga as banned still. Grudj getting ban is alright but Olga disturbs a lot.