dmg on sro is never fixed, you will find that your dmg will have a lowest and a highest point
this depends on your physical/magical balance, attack rating and reinforcement present on your equip(i think there is an explanation for that somewhere on this forum)
adding an Imbue, gives you extra effects(Rouge imbue will just poison, no other dmg addition)
for CH imbues, they give the dmg imbue and the side effect(burn, frostbite/frozen, shock)
[Only registered and activated users can see links. Click Here To Register...]
that is a little explanation about Damage calculation
its from 2009 so it may have little tweaks(like SRO-R dmg formula change)