If I may make a humble observation, on nearly every campaign that has had custom missions that I've seen so far (IDSL, AOTK) there is always an outcry at the beginning that the server settings are too difficult, the missions too hard etc. Yes, they are harder than the stock missions. Why? Because once we are a few weeks into a campaign, people have found their starship feet again. Everyone is 'rusty' at the beginning of a campaign, but by the end of it, the missions seem too 'easy' and people start complaining that they can't be bothered with another boring AI patrol that offers no challenge.
Its a learning curve and these things take time to settle. If you are finding the mission difficulty 'normal' at the beginning of a campaign, its almost guaranteed it will be far too easy once its been running for awhile. Also, there are a large number of players with different skill levels who play on a server and you can't please everyone. Some will always say its too hard and some will always say its too easy. Regardless, however, it should be enjoyable, nonetheless. All I say is, give it a chance, try to see if you can find ways to beat those 'difficult' missions, its a strategy game after all, not just a 3D shootemup. At the end of the day, the true measure of success is if you've had fun or not, nothing else. If it becomes work for you, then by all means, dont play. But winning all the time isnt much fun either. Just my thoughts on the subject, hope no one is offended by anything I've said.