First: Love that the Dope is indeed such a terrific place to bring speculative fiction ideas for fleshing out, etc. Always have enjoyed that aspect of this place.
Second: I encountered quite a few EMT and Paramedic folks while I was active who stated quite clearly- some almost angrily- that when they were not on duty they would never engage in a scene needing their help. That they did enough while AT work. Didn’t want to screw up a family vacation, etc etc. My inner response was always " fuck you cupcake. You have skills and experience that could make a difference here, right now, but don’t want to mess up a day out with the family? Then don’t be in the EMS business. " I’ve encountered/ witnessed a handful of emergencies and have always stopped. My god. I’d want someone ELSE to stop for me !! Good link on Good Samaritan Laws, how they work, etc.
Third: Asking for a situation where minutes count isn’t in of itself unbelievable. People DO witness trauma in real time. People DO drive by a few moments after an accident has occurred. That’s life. I caught a woman who slid from her folding chair as a grand mal seizure set in.
Here’s one that fits your scenario. I was driving north on the NYS Thruway. I was being someone clearly drunk or having a medical problem. ( This was around 2001 and so texting while driving was not a thing yet. Not really. ). I called 911 and talked to the State Trooper, explaining the situation. They sent a few cars to try to catch up to us. One from behind, the other one coming south towards the Harriman tolls area with the intent of turning around. The person- incredibly- didn’t crash into the toll area barriers, but instead blew through. No more than 2 miles past the tolls they went unconscious. Swerved hard into the Jersey barrier in the center median, deflected and headed for the shoulder, where the car rolled quite a few times. I watched as the driver was partially ejected through the driver’s window, but was held in place by her seat belt.
Pulled over, cursed, got my stuff and ran over. To find a woman dressed in the classic bartender/ waitress outfit of white shirt, black bowtie, black pants. Unconscious. With not one but TWO penetrating wounds in her skull. ( These from the torn area around the window of the car. The metal framing crushed and tore as the car rolled and pierced her skull twice. )
ABC’s. I pulled her out of the car, laid her out and found her to be breathing. Reeking of alcohol. Just…reeking. State Trooper got there a moment or two later. I asked him to call for a helicopter. In the time it took the helicopter to arrive, and as I knelt there holding her neck in place to maintain good cervical alignment, her breathing slowly became more labored and her face and eyes started to darken slightly. This from the two small penetrations into her brain.
She was alive when the helicopter lifted off. She didn’t live out the night.
So. I was RIGHT there, with training and tools. And there was fundamentally nothing I could do. Consider this kind of thing when you structure a trauma situation that could or could not be resolved using magic.
Now to your scenario.
Here’s the thing. You want some level of verisimilitude here or you wouldn’t be asking for input. Handlebars ram into lower abdomen at 73 mph? Yes, you can have tears and ruptures etc. To whatever degree of severity you want to create. But the penetrative trauma likely with even a 25-30 MPH motorcycle accident ( that’s with some good quality leathers on, zipped up and padding the front of body ) are still significant.
So. Our hero, who we might name Kelvin cause he’s one cool dude, goes over the high side. He’s got leathers on and yet as he and the bike are rolling, the handle bar/ gear shift metal bits ram into his abdomen with enough force to do major damage.
I and my mage stop by 4 minutes later. If Kelvin isn’t dead already from the odd ruptured aorta ( a fabulously rapid and brutal way to die ), he will likely have significant enough multiple internal trauma that obeying the A.B.C.'s of First Response would mean that I’d establish a sound airway first. Let’s say Kelvin is - miraculously- conscious and responsive. So, Airway is good. He’s able to speak so Breathing is fine. Circulation is next. That’s mighty vexing to accurately assess down the ravine where he was thrown. ( Because how unsexy would it be if he crashed at the edge of a Wal-Mart parking lot?? 
)
When I was riding I had a jump bag. Within that were the basics of first aid blood flow control- bandages, latex strips, nitrile gloves, etc. Oxygen, mask, air bag, cervical collars, etc. My mage would have given me the right size collar, because you know…it’s a mage and knows things. In assessing circulation, I’d want to basically cut away all of the patient’s clothing but since this accident happened on January 7th just outside of Scranton, PA and the ambient temperature is 22º f, that presents its OWN risk set. So I do an in-clothing assessment. I find extreme pain response and tenderness in the rib and abdominal regions. I find blood pouring out of the left sleeve of the leather jacket from an open fracture of the left humerus. While it seems fairly certain that Kelvin’s gonna die of internal bleeding fast, that fast bleed on the left arm could do him in within 10 minutes as well.
This mage, is it all-knowing and all-powerful? If so, then why is it relevant that I’m an EMT instead of, say, a guy who delivers Dunkin’ Donuts supplies every morning? If the mage ISN’T all- knowing and all- powerful, how much info do I need to provide to said mage so it can do its magic?
I’m not trying to be difficult here, but providing a device in a story that’s magical kind of removes most if not all of the dramatic tension from a situation like an accident. I could be the lord master of Paramedics or the greenest of green newbie E.M.T.'s. It wouldn’t matter if I had magic on my side. Within 1 second the internal damage would be magically healed and the bone fragments resolved and vascular damage healed in the arm. No drama there.
What are the limits of this mage that my being an E.M.T. becomes useful, relevant or dramatically interesting?
