Do remember that randomization can frustrate players for the logical reason that the best item might be impossible to ever obtain. This is the problem games like Diablo are most famous for. You have to be very careful that the end game items do not become as good as impossible to get or you will lose players and map ratting. After all we all remember the "Diablo II HR" problem where outside of exploits and cheats it was as good as impossible to get a High Rune fairly.
For example, say you have an item that adds 1-100 of all 3 stats. The chance of you getting the perfect roll of one of its stats is 1 in 100. Since these are independent rolls we can multiply them together so the perfect item has an 1 in 1,000,000 chance of dropping. If that item type drops once every 10 minutes that means that on average a player will need to look 166,667 hours or 19 years of continuous game time to find it. However that is just so that half the players have it, the other half could spend much longer (even eternity) finding such an item.
For the best gear in your WC3 map players should not need to invest more than 12-24 hours of gameplay time to get. This is because of the fact you are competing with other maps for player time so if stuff becomes too much of a grind to get people will rather play something else. To do this adopt Diablo III 2.0 techniques of lowering random ranges, improving drop frequency and allowing people to re-roll bad affixes separately. You still need to go further than Diablo III 2.0 however as that is a separate game so spending 100+ hour for best get is acceptable while it is not in a WC3 map.