I've had plenty of exposure to dealing with stumps. Burning has not been one that has gone well. I mainly dig them up and bury them.
That started out as a THREE tree clump (the trees had been cut by someone else; likely years previously): small, medium and LARGE. I got all but the LARGE stump pulled using my B7800 and truck. LOTS of manual work: digging by hand; using a splitting maul and a hydraulic jack to split the medium and large stumps apart. I finished it off with a rented excavator (small). Oh yeah, I managed to drop my B7800 next to the stump, wedged and had to get my truck to pull the B7800 out! (lessons that taught me the value of renting excavators to dig with, renting bigger ones at that!)
I've done MUCH bigger stuff, but only using a larger excavator: NOT going to post those pictures!