Please take note what was posted in the newspaper.
Quote:-- Gang wars will take into account the strength of your gang. Players with many members close to their level will benefit, having a ringer will not be factored in.
-- Defenders who are in gangs will have a slight "back-up" modifier. Players attacking gang members on their own or while in a group will be at a slight disadvantage since you are attacking on "the defender's turf". Gang wars however ignore this advantage and follow the previous rule.
There are a lot of variables in combat, too many to place blame on one stat like resistance. I must have misunderstood your post of, "if my opponents are tougher, the damage will be less". Stats are important, but don't forget level and the notes about gangs.
When you attack someone, you are going to their turf. If they are in a gang, they might have a "morale boost" to their stats. This boost is due to many factors. Remember, you are going on your own (even if you are in a gang) to attack a gang member. They will be in their comfort zone while you will be in an area you aren't familiar with.
If you want backup like they get, you'll need to start a war with them. This will give boosts to both sides, but having a much higher level character in a gang might actually lessen this boost since they are considered a "ringer". Who knows, this boost might not even make a difference. But if both sides are evenly matched and somone brings in a ringer, it might help the other gang.