To me it is not Samoa Joe himself, it is the situation he was put in.
Last year, he was jobbed week in and week out to Kurt Angle. The year after it, the same. And this year, the big victory of Samoa Joe comes in his 1002th match against Angle, in a lousy MMA like match and one in which it was obvious he was winning, as his career was on the line.
Then, Joe wins it in a very anticlimatic way, and TNA, instead of bringing a good opponent for Samoa Joe, I don't know, Booker T, Sting, back Jeff Jarret, AJ Styles, elevate Robert Roode once and for all, no, they give us Kurt Angle again and...Scott Steiner.
Steiner and title matches just don't go. He failed with HHH, damn HHH, the drawing machine HHH, why would it be any different with an unexperienced champion like Samoa Joe?
Besides, ratings are not low because of Joe, they are low because of the pathetic Sacrifice PPV they are hyping.