The frequency sweeps on your loudspeaker look good but that is not the whole story. The averaged results looking the best. They may sound good but I'm guessing not even in the same league as bigger full range speakers that could blend in a sub a little better. Not having your speakers to listen to puts me at a disadvantage but let's just say you didn't like the sub in your particular application but I would not want to paint all systems with that broad brush.
Why I'm not adding a sub to my 2-way monitors for music
I've updated my blog post with more data, more analysis and the conclusion that in my particular case I do not need a subwoofer. I encourage everyone who is on the fence about adding a subwoofer or not to read and comment. I think that either way you'll be able to make more informed buying and configuration choices.
Everyone's situation is different but I hope the post helps you get to the right conclusions.