I think it is the Han special abilities and the fact that their range units are so much more powerful that make the range game so deadly. but I do agree, as it stands right now, there is only one way to counter that and it is with Han archery. I was actually thinking about how things could be toned down and I don't believe that modifying LoS is the answer... If we argue that units block LoS will significantly tip the scales to the other side, where cheap roman units just walking in shield wall formation will just be devastating.
I think maybe a move or shoot type hinderance will be the answer, or severe shooting into combat (or through combat) penalties would work. It may be as easy as removing 2 dice instead of 1 for shooting through units/terrain and into CC.
I also agree that the Fireburst is a little over the top, and looking at the Egyptian Death Touch, I think 1 base length for Fireburst will be the answer. Of course, those two kinda go hand in hand since as a Roman player, Fireburst is really one of the major ways to combat the Han range game.
From reading the forums, it looks like the game creators don't really believe in statistical data (let me remind you, that I work with statistics on a daily basis

) and although they gathered data, which I assume told them that the range combat needed "something" done with it, they chose to ignore that data and instead do it the old fashion "marketing" way and promise improved units to deal with the shooting in the future. It is an easy way of making a quick buck, and it is also a sure way of losing your customer base's trust in your ability to support a good game.
Regardless, I will support whatever Ken decides to call house rules, and I am not yet at the point of giving up on trying to beat the Han players at their own game
Cal