Even IF he was stronger than Minato, that doesn't instantly put him in the top 10. The top 10 is getting really crowded with some seriously OP Shinobi now that the manga is nearing it's end.
We're gonna need to see ALOT from Tobirama if he is to be in the top 10 and I just don't see him getting that much panel time with everyone else at the battlefield. Keep in mind that Kishi needs to invent jutsu's for him, and that takes alot of time, effort, and creativity at this point. I'd say he'll get top 20, maybe 15.