d20 simply IS NOT balanced. There are many ways to acheive a Viking-like class without resorting to d20 HD.
If massive combat ability is what you're after, then consider giving double bonuses to their rage (+8 STR, +8 CON). That alone will make them a more powerful barbarian-type of class.
One skill point per level is a bit harsh. Give them half what the barbarian class would get, and don't offer the fast movement to your vikings. Those changes MIGHT be enough to consider the viking class more balanced, but it would be best to see how things work and adjust from there.
You seem to have thrown in a d20 HD without considering game balance at all. How about basing your viking off the barbarian class and making smaller adjustments (as I just did), rather than trying to go with a d20 HD and then looking for ways to compensate that are also unbalanced.
I could make a wizard with d20 HD too, and to compensate will only let him cast fireball spells and nothing else. NOT BALANCED! Keep it within reason! If your whole campaign is like this, that's fine, but I don't think it's balanced IMO.
*edit*
You asked how to make your berserker stand out more from the barbarian--how do you see the two classes differently outside of combat? Answer that question and use that to help create distinctions. Myself, I don't see a lot of differences at all, so I think the many suggestions to base your berserker-type warrior off the barbarian are more appropriate than trying to create a new d20 HD class.