How hot is your oven? What temps can you say you are cooking at? Im assuming you preheat the stone for a while too?How long is your bake time when the crust is still not done,but the cheese still seems to break down or burn?
As far as cheese goes,Im using store brands I can find.Where I live,its not a dime a dozen...hard to find anything good in my neck of the woods.
I found that using whole milk mozz that I cut or shred myself gives me the best results.
Using pre-shredded cheese from the bags always burn a little faster,at least in my experimenting.I do not know why,but I do know they have an anti-caking cellulose agent,to prevent sticking in the bags,that might lead to premature burning in hot ovens.
The brands I have used,but not limited to,is Kraft part skim block cheese I shredded myself.I did not care for it at all.
The whole Milk brands are Polly O,Sorrento's,and the Great Value Brand from Walmart.
So far,Sorrentos and the Wal Mart brand is my favorite.There was another brand I bought once from a store but cannot recall the name of it.I remember it being yucky though.
Also,there is another shredded bag of cheese I have used called Sargento's.I have not found a whole milk block in that brand yet,but am looking for it.The sargento brand is part skim but seems to hold up way better than the kraft version.Just letting you know not to confuse Sargentos with Sorrentos.
Reason for freezing the mozz block cheese,is that it helps to shred so much better.When it begins to thaw,and you start shredding it,it cuts with ease and no mess like warmer,room temp cheese does.
You cannot shred it fully frozen,but when it begins to thaw,you can keep doing so until you get just about all of it done,and none wasted.Warmed up cheese sticks to everything and gums up the shredder.