Abilities like logistics, artifacts like Sandals of the Wanderer, and tagging map elements like stables or rally flags are the only move boosters I know of. I read somewhere that heroes without units can move further than those with armies, but I haven't observed that in my own games. Previous Heroes games set movement to the slowest unit in the army, but again I haven't noticed anything like that. Regardless, those are impressive numbers and perhaps reflect an older version of the game. I don't think I've ever had a hero with more than 50 movement or so, fully kitted and buffed. One thing I have encountered was a mysterious and persistent 25% penalty to mana costs, but only for my avatar and 2nd hero, both brought forward from previous maps. In a similar vein, the only thing I can think of is that some of your heroes got some kind of move boost from a "Week of the..." that, through a bug, lingered on after the week ended and/or on to the next campaign map.