The help is irrelevant. It would be like citing the significance of Fisto, Tinn and Kolar to the outcome of Mace and Sidious.
The main point is in the circumstances and what they mean. A low point in mental and physical energy causes GM Luke to drop several tiers. Mundi is in that position against Grievous, and lasts a while on his own off panel.
Then you have to factor in Styles. Grievous is a cyborg with rotatable joints and vertebrates wielding three lightsabers. This is unseen territory for Mundi,
On the other hand, Jinn is fresh against maul with the latter sporting a classic stance with a training weapon.
Qui-Gon had barely managed to scramble up the rampway and into the interior of the ship before the hatch sealed and the Nubian began to accelerate. He lay on the cool metal floor of the entry, his clothing dusty and damp with his sweat, his body bruised and battered. He breathed deeply, waiting for his pounding heart to quiet. He had barely escaped with his life, and the thought was worrisome. His opponent was strong and had tested him severely. He was getting old, he decided, and he did not like the feeling.
Junior novel:
He made it! "Qui-Gon's on board, " he told Olie as the ramp closed. "Get us out of here!"
Without waiting to see whether the pilot obeyed, Obi-Wan started for the main hall. The young boy followed him. They found Qui-Gon in a dusty heap just inside the entry, covered with sweat and breathing hard. I've never seen him in such bad shape after a fight! If we hadn't gotten to him when we did...
Qui gon is running at a pace that allows 9 year old Anakin to stay behind in close proximity. And Anakin isn't breathing heavily or collapsing as soon as he gets on the ship.
Jedi can spar at high intensity for hours without breaking a sweat. Maul actually had a wound and had been fighting random ****ers before taking Jinn on, you don't hear him whining about it.
But yeah Fisto has the best feats of the B-Team, Koon and Jinn, due to handling Greivous (even chopping off an arm) and legitimately blocking a few Saber blows from an all out Sidious (opposite Windu of course).