You are aware they made the conference finals in the superior conference this year? If they couldn't "mask him defensively" they would've lost to the Clippers in rd 2 because they were 1 of the best offensive teams in the NBA. Also Harden not being a good defender is 2013-2014, it's common knowledge he was pretty solid this year despite having to carry an insane offensive workload. When your 2nd best player is Trevor Ariza for most of the year, your D tends to suffer.
They made the conference finals and then were completely blown apart... They were outclassed by Curry and Klay and it was all because Beverley wasn't around. When you are getting dominated because you don't have a lesser known PG it speaks volumes about Harden's ability to defend. His defense isn't as bad as that funny YouTube video but he's still below average because he has no energy left on that end of the court after using it all on offense.
Houston was loaded this year IMO. Obviously injuries hurt them but Ariza is one of the best SFs in basketball and perhaps the top defender at that position. Howard is a monster on both ends. Two legit NBA-level starters at PF. I don't like Smith but he'll start for a lot of teams. Beverley might be the top PG defender in the NBA. Corey Brewer could start for a lot of teams.
The Rockets had so many strong defenders going that they were able to mask Harden's weaknesses and let him do his thing offensively. When Beverley went down they were not able to do that and it opened up holes for opponents. To me I'd rather have a complete player. To each their own.