Honestly, i dont see what the massive issue is here with Garrosh. You wont like him at the start of Cata because of his current WotLK persona.
It took Blizz from the start of WotLK, right through Ulduar, TOC and ICC to develop a widespread hate amongst a majority of players for Garrosh. Same thing will be needed for anyone to gain any respect for him.
To put that point into perspective, no one really hated Garrosh during/at the end of BC, simply because he had no story at that point (unless you dislike whiney emorcs ), and even at the start of WotLK he just seemed a little hotheaded. It wasnt until a little later with this interactions with Varian and the schoolyard taunts between the two that we realise Garrosh is a dick. Same goes with Varian, playing primarily from a horde perspective personally, i hated Varian until i read up on him allowing Varok to depart with Dranosh's body in ICC. Massive redemption points for Varian there, all in one act of kindness.
I dont envision a mutual respect between Garrosh and Varian like there appeared to be between Dranosh and Bolvar at the Wrath gate (personally loved that scene).
Have faith in Blizz that, if they dont give us a half decent character, they will at least give us a good story along the way