does duskblade and stormrazer damage stack?

Yes in the sense that both give a damage increase. Stormrazor will modify your basic attack by a %, and duskblade will deal flat damage. Stormrazor won't modify the duskblade damage though.

Duskblade is a on-hit effect, it will be added to the damage of your auto-attack Stormrazor enables you to crit on your first attack