I just got two Succubi in a row. One has War God (increases attack by 10%), the other has Stone Skin (reduces damage taken by 5%). So... Which one should I keep and which one should be eaten? :-)
War God is what I would keep. That is a good skill. As was said; however berserk is a better skill. Keep in mind, however, that War God is better than 75% of the other skills you could get and not worth a re-roll unless you are ready to spend 1500 gems . If you spend 1500 Gems, you have more than a 50/50 chance to get something better if you accept anything better. If you want to get one of the best skills, at a high level, you'll need to be willing to spend 30,000 gems to have the odds in your favor.
Remember, there are many skills and 5 levels or each. A re-roll for you could be much worse.