Those are reasonable. With many questions having twenty opinions, if you took twenty questions together and each person got one MHO from the bunch, each would have a percentage of only 5%. So it can be hard to get higher numbers. There are some people on here that do not answer much unless they have a really good opinion to put forth. @Ozanne is an example of one who consistently rates high with her opinions. But the ones who just shotgun worthless opinions to get Xper points, end up with lower MHO percentages. Honestly, if someone has reached the higher awards like Guru and Master with lower MHO percentages, then they have earned the level by answering everything quickly without trying to give the best advice.
Of course, if they awarded the level based on your MHO, I could be a Master now. :-)