If you want to believe that their form of Tungsten is exactly the same as it is today, or that it is used in its raw form, then there is no problem. But there is no reason why this metal could not have been modified in some way, especially considering the fact that this is in the distant future. Like durasteel, the tungsten is probably not in the same form that is reconizabe today. My guess is that Tungsten is the element that they used because of its high melting point. From there, the engineers probably did lots of modifications.
If we used literal durasteel and tungsten, they cannot really be compared to each other in equivalent strenghts. Thus by the very way that the armors are compared, we know that this cannot be just ordinary tungsten or durasteel. Anyways, we must not equate strength with melting point.
Physically the ships would, out of *neccessity*, be made out of far stronger material. Accelarating at hundreds of klicks per second puts quite a bit of strain on any craft. And besides, if one actually belives that this is the exact same form of tungsten used today, than there version of durasteel must be some pretty weak stuff. Due to the low masses and great strength of the ships in the universe we know that they do have some pretty advanced materials. As Wc3 stated, They have an entire science whose focus is that of advanced materials. A science that rivals the pace of todays top starfighters. So ... err ... it would really be starnge that they are using a metal exactly the same way that it was used six-hundred years prior.