If you could get some kind of gap between the metal platform and the quarry tile, you could probably prolong the life of the tile and help bolster the top heat a bit. If you always keep temps below 800, then something like crumpled aluminum foil might do the trick.
Right now, you've got an incredibly intense heat hitting the platform, which, in turn is conducting heat to the tile. Air, even if it's a fraction of an inch, will give you deflection. In most bottom burner scenarios, some deflection is good.