I don't remember anyone backing Darui up, Samui and her brother got merked within minutes. I'd say they were in the way, but even I have to admit. If it weren't for them getting sucked in by the gourd e wouldn't have figured out the trick to the tools.
Samui and Atsui were backing him up, if they weren't there, firstly he would have been sealed like you said, but second they were there to occupy K/G. So if they weren't there in the first place Kinkaku and Ginkaku would have ganged up on Darui and killed him even quicker.
Once he went into bijuu cloak form shit went down, Darui got stomped and the entire division was losing, and he needed the third-party sealing pot to seal him in the first place. Here's one example of the entire division backing him up:
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Pretty much everyone was backing him up in that division, he stood no chance against Kinkaku and Ginkaku alone so it's no really something you can use to hhype up Darui's power. Plus to top it off, to mention 3rd party, not only did they need the pot but Ino had to switch to his body to answer the calling of the pot to be sealed in the first place
