Comparing just those percentages would be a bit misleading, as OLC's business model has been very successful so far. If you look at the flat increases, TDR has been showing stronger growth than USJ (actual number of increased visitors) in every year except this year. WWoHP is obviously a huge deal, but I fully expect TDR to receive a similar or even higher increase in attendance when they open their Frozen-themed port at TDS.
Fiscal Year Attendance Figures for Tokyo Disney Resort
2014: 31,377,000 persons
2013: 31,298,000 persons
2012: 27,503,000 persons
2011: 25,347,000 persons
Fiscal Year Attendance Figures for Universal Studios Japan
2014: 12,700,000 persons
2013: 10,100,000 persons
2012: 9,700,000 persons
2011: 8,500,000 persons