.. you can't block specials completely in MM6 like in MM7 and MM8 - it made lots of spells useless (and broke the game) once you got Prot. from Magic. I think it's part of what made MM6 much tougher. The sheer amount of detailed dungeons (the riddles, puzzles and well hidden areas (need only mention the Shadow Guild)), HUGE dungeons and crazy-sized mobs. (Snergle's army, the undead army of the Temple of Baa, the throngs of Magyars inside Castle Alamos to mention a few.)
Also the presence of the unblockable energy damage from Gold Dragons, Droids, Warlocks, Power Liches and Guardians of VARN makes MM6 an unfair comparison to MM7 and MM8.
Oh, and did I mention the radiation inside the VARN vessel - it still creeps me out.