If it is too sweet for you try omitting the dark brown sugar. I know it doesn't seem like much and I know people will tell you it will ferment right out but it definitely does effect the perceived sweetness of a GB. If that doesn't cut it look into recipes for a scratch GB as the tin's artificial sweeteners might be what is causing this problem for you. Or if you think it might just be a balance issue you can always put in more fresh ginger - my base recipe is somewhat similar to GravityGuru's but I use double the amount of fresh ginger and it works well for me. Also, a little chilli is known to extend the tail of the ginger bite which might rectify some of the issue for you (a little bit goes a long way, IMO).
Oh wait, when you say sampling what do you mean? SG samples? Or early bottle samples? If SG what is it sitting at?
In any case, once the GB is fermented out the ginger will only fade with time.