Current draw from the batteries is derived from the wattage setting. Not the load. MXJO's would last longer than vtc4 due to higher mah. At 50 watts you would be using ~13.5 amps plus a little more due to losses in the converter. The load resistance doesn't have anything to do with it. A 30 amp battery wouldn't help you in this case because you would not use more than ~16 amps even if the battery is down to 3.0 volts.
Well said and right on point as well!
But I don't know MXJO's from a hole in the wall.
What it says on the battery wrapper or on the website you ordered them from may not match the battery that is under the wrapper.
I could take a Samsung 2500 mAh, 20 amp constant rated battery, slap a new wrapper on it and say it is a 4000 mAh, 40 amp constant rated battery yet underneath it is still a Samsung 25R. 2500 mAh at 20 amp continuous discharge.
Me, being a paranoid old fart, I am not trying a new battery until the Flashlight Folk have them in hand, hook them up to all their fancy diagnostic gear and tell us what exactly is under the "Hood".
Or wrapper in this case.