First of all how they gonna screw Minato? Any Bijuu Dama either gets tanked or flicked back by Kurama's tails, at worst case Minato can redirect them via Guiding thunder.
They don't have enough firepower to put him down, Kurama Avatar's tails tanked Juubi's laser which is many times stronger than 2-7 tails Bijuu Damas combined let alone one by one.
Now to answer your last question, remember Hachibi's (that should be more durable than other Bijuus aside from Kyuubi) was heavily injured (to the point that Bee couldn't maintain BM any longer) by his own regular Bijuu Dama which nowhere near the level of Kurama's regular Bijuu Dama.
Conclusion : Kurama's regular Bijuu Dama which takes almost no time to form can one shot any of Obito's Jins & force them to go back to base (being non-factors)
1- Minato's chakra reserves <<< 6 bijuu's chakra reserves. Sure minato can keep dodging and tanking their atacks but he would fall before the others after a short period of time, since he would be tired of dodging atacks from 6 bijus at the same time.
2- Minato is not gonna dodge and tank all day, and when he takes his turn to atack is when the other bijuu take their advantage to hit him, since Minato's only way of hurting bijuu is TBB, and he has to become stationary to make that.
3- They don't have the fire power to take him down with one TBB but Minato's avatar would be gettin weaker after his chakra starts running out, he's not an edo like in the war.
4- That was not the hachibi's regular BD, it was a surprise atack to the juubi, so it had to be done fast, Killer Bee didn't have time to make a bigger one, Minato would have the same problem in this matchup.
5- So the bijuus are having a hard time hitting Minato but Minato is the one that's gonna have the hardest time trying to take down 6 bijuus.
This becomes a battle of durability, and Minato's chakra will dry out before the other 6 bijuus.