No, it should not get a +1 bonus for mark damage. That would cause it to get +1 cost (see Hammer) and slow it down, which is not wanted in rushes.Please leave this card as it is. Interestingly, there was an Other weapon being suggested that boosted w/Fire Mark though. Let me see if I can find the link.Here is it : Arquebus | Blunderbuss (http://elementscommunity.org/forum/index.php/topic,21342.0.html)
I like this, good cost for good damage, some may say it's op, but that's why its an other.