I haven't been to this site very often for a long time, but I've come back to the ENTJ forum, I read all the new posts recently, and all the relationship problem threads about ENTJs include INFPs or ENFPs. Has anyone else noticed this? interesting.
It has to do with the Te / Fi clash, considering Te is the dominant function in ENTJs -- whereas Fi is the weakest function -- the one ENTJs are most sensitive about presumably. INFPs are the reverse. Similarly, it's my understanding that these type of Ns are more likely to pair with other Ns. Hence xNFP complaints about ENTJs.
There are problems in all relationships. The important thing is whether there are more problems than not. People come and ask for advice on the problems they are having, this may make it appear as though their relationship is mostly a hassle. They wouldn't ask for advice on what is going well in their relationship, and if they wrote about all the good, it could just be considered useless and a waste of time to read. They come, state their issue and ask for advice. IMO, the fact that they are seeking advice means they are putting work into the relationship. Work is required in even the best of relationships at some point.