What if Tobi hides underground then he goes to the surface every once in a while before his intangibility wears off so he can just go underground again? Meanwhile, Minato has to hold off the 6 bijuus or Gedo Mazo.
As for FTG away from the TBB, how big would the blast radius from 6 TBB be? If it would cover the entire battlefield, then wherever Minato teleports to in the battlefield to try to avoid it would still be in the blast radius. That is, if the kunais didn't get wiped out due to the explosion. Ofcourse, Minato is an Edo but it will take some time for him to recover while the Bijuus get pulled in by Gedo Mazo since the blast might also destroy the rods that controlled them. While Minato regenerates, Tobi (having remained intangible during the explosion) could be warping himself to Minato and use Human Path. Unless Minato could use the barrier on 6 TBB from different angles but if they still detonate the entire battlefield, it'll end up the same. You should have stated were the battlefield is since in this fight, it's a big factor.
If the area is larger than the explosion, let's just hope Minato actually placed a kunai away from the explosion's reach or atleast so he can teleport it away far enough to be out of its reach. Not to mention, it could be six at the same time so it'll take up 6 times the area than one TBB. Or 6 in different places that could be hard for Minato to guess where to teleport to safety instead of teleporting inside the explosion. If Minato is allowed to use Kunai that he has at home, then it would be a huge advantage when fighting those who have attacks that have a huge radius.
Since Minato is an Edo in this fight, it does prove to be a huge advantage. I don't think it gives unlimited chakra but atleast he won't die if his chakra runs out. He'll also recover from all forms of damage. Honestly, if Minato wouldn't be an Edo in this fight, I don't think he would have many chances of victory. Especially if he doesn't have kunais outside of the TBB blast radius. Since he's an Edo and could recover from it, he has better chances if Tobi doesn't decide to use Humn Path while Minato regenerates. It also depends how long it takes to regenerate.
I still think Tobi would win with High difficulty. It would suck for Minato to have to focus on the 6 tailed beasts and Tobi all at once. They aren't coming one on one and they'll also be coordinating their attacks either as diversions, defense, or full assault. If Minato gets distracted to the point where Tobi comes out of the ground or warps to him and stabs Minato with a rod, then Minato would be under his control. If it were Minato only concentrating on Tobi, then he he could possibly evade that but he also has to focus on the tailed beasts or he'll get wiped out.
The way to defeat Tobi and Minato is to catch them by surprise. Tobi won't win 100% of the time though. Minato could place seals on the ground if he's able to and hope that Tobi gets near them so that he can FTG to Tobi and catch him by surprise if Tobi isn't underground. Tobi could be using the tailed beasts as diversions or coordinate their movements and attacks with his own to catch Minato by surprise and stab him with a chakra receiver. He could then proceed to use Human Path while Minato is under his control.
Either side could win but in my opinion, Tobi currently has higher chances to be victorious.
