The wikia's damage calculation is much more versatile because it includes the resistances of the target and can be used for either weapons or spells with out changing anything. If you do not want to go through so much just put the calculation in a spreadsheet or something. Then when ever you need it you can just fill in the characters stats, buffs, and the weapon/spell's min and max damage

Weapons also have their own skills which depending on the level it can boost from 10% to 65% and only close combat weapons are affected, others like Relevant Stat, boosts water, Class Bonus. such effects modify this variable.

It is not seems that Calculating damage is so hard, you can do is Just remember that the spell or weapon you use gets a +%damage increase from its corresponding element and add in the +%damage from your gear and buffs, then when that is calculated just add +damage from gear and buffs.
Here are the specific details of the death of computing:

When you lvl(Dofus gold) 5 ghostly claw casted by an osa with these stats/buffs, you have 9-12 damage and 100 intellegence, +50% damage pet +10 damage
Even it having to write nothing down when comes out to 32-40 , but you can Calculating damage as: min = 32 = (9+150%)+10 ormin = 32 = (9*2.5)+10 and min-dmg = (9*(1+((100int+50)/100))+10 = 32 as well