To say actually a space marine can wield two thunder hammers but it depends on how strong he is. Normally it's a chapter master that wields them.
There's a reason why no one dual wielded weaponry in history: It's stupid and it doesn't work. Not even Kharn the Betrayer uses dual melee weapons. Here's why:
http://2.bp.blogspot.com/_CbSWEUnVC...S8/JbzrGyJ8hL0/s320/Darksol's+Gallery+580.jpg "realism" in war 40k?
"Boohoo it's historical therefore invalid"--Wrong. Watch the video and understand why dual wielding melee weapons is a terrible idea. It includes not just historical examples, but also common sense.
I can understand your point on the topic. But one thing to consider, at least for historical accuracy, troops didn't have that great of body armor. A shield was ideal for any soldier armed with a sword, axe or whatever. So in terms of historical accuracy I can agree with you there. But in the world of Warhammer 40,000 there are super human soldiers armed with weapons taht could smash humans into dust with one hit. I think characters like the Space Marines and Orks would be best suited for duel wielding. Where as the Eldar, Imperial Guard and Tau would not.
Eldar can actually do pretty well with dual wielding IMO seeing as they move faster than just about everything.
I don't think you understand the point made in the video and the point I stand with, that being dual wielding is simply ineffective and it doesn't work. You're able to attack at the same speed and with greater power with a single weapon, and still have a free hand. "It's faster" How is it? Please scroll up and watch 'A point about dual wielding' to understand how it isn't faster.