I haven't bothered combing this thread for inaccuracies yet, since I'm busy doing the turn. What I will say is this much;
The Arcanan Empire at its height reached Renaissance-level technologies verging on steampunk. The problem is that a lot of it relied on magic and power supplied by the Master Wizard, and the bigger problem was that the stability of the empire hinged upon the fact that the Master Wizard could basically wipe out whole villages with a flick of his fingers if he so desired. This sort of thing encourages obedience.
The problem is that the aforesaid technologies were reached only during the very early part of the full Empire, at which point there was something of a dearth of intellectualism and free thought. Technology stagnated for a few hundred years, and was highly localised - the best technology all remained in the central continent of Imperia, where the capital of Empire was. Most of the rest of the world was left in pre-industrial and sometimes even dark ages underdevelopment because it was not worth developing. Why bother improving the conditions of slaves when all you want is their natural resources to fund the lifestyle of the core citizens?
When the Master Wizard died not only did all of the spells he supported (save the Spell of Mastery) start to unravel and fade away, invalidating many of the pieces of technology that relied on it, but the everpresent threat of arcane Armageddon vanished with him. Once it was discovered that new wizards could not be trained to replace him because of the Spell of Mastery it fell to the mundane Imperial legions to try and keep control. Now, you would think this might actually cause an improvement of technology because of the need for competition. You would be wrong.
The Imperial Legions were too few in number to stop uprisings across the whole world, but they were still large enough in number and powerful enough in equipment to crush any one rebellion. The lack of infrastructure across the remainder of the empire was what led to its collapse, as all the underdeveloped regions stopped paying taxes and started fighting amongst themselves for dominion when they realised the Master Wizard would no longer blast them with fire from the sky. In these outer regions, especially the continents of Northbrand and Southrel, the legions simply abandoned them to their own fight and without the stability or infrastructure to engage in serious research warfare remained pretty constant and things just deteriorated further.
The central continent has suffered a similar fate; as the Old Empire withdrew its borders decade after decade, control and civilisation fell to the individual territories. Some were better at maintaining their fare than others; many descended into anarchy and others were rotted from within by decay and corruption. In essence, five centuries of decadence, infighting and stagnation have been killing the whole world.
So technologically, the world has regressed heavily over the last thousand years. But once, it verged on steampunk.