I have been playing TapX since I got my hands on the osu tablet back when it first started shipping and have had a lot of success with the style. All the top ranks on my profile (https://osu.ppy.sh/u/1853777) were achieved playing TapX. I can stream 300 BPM and can play relatively fast. However, I feel I have reached a road block. I have a lot of trouble playing songs like Catastrophe(https://osu.ppy.sh/s/72740) on DT as well as a few other songs. I watched Yamemasita play today, one of the best TapX players in the world, play today and even he begun adapting an alternating style. 
To the few out there that do play TapX, is learning to alternate a must once you start playing very fast songs? What kind of songs would you recommend I start playing to better my ability to play if it is?
To the few out there that do play TapX, is learning to alternate a must once you start playing very fast songs? What kind of songs would you recommend I start playing to better my ability to play if it is?