If you add more aim to a dueler, then he will have more chances of slaughtering adventurers and builders whether in attacking or defending cause dueling doesn't involve soldiers and duelers only.
And besides, 25% more aim (50% with premium) isn't fair at all cause it can be used for both attack and defense whereas the added tactics for soldiers only come into effect when they are defending. Soldiers however have more survivability because of more health but that has nothing to do with the hitting value.
If anyone's unfair in terms of dueling, that would be soldiers. They have added tactics, health, and the ability to use weapons 3 levels ahead of other classes and those would double if they use premium. However, there are no apparent measures in the other classes that would make them beat soldiers in terms of dueling advantages.