Its been more than a year now i started using Windows phone (Nokia Lumia 730) and found "Tubecast for YouTube" as one of the best YouTube client to watch videos and for casting YouTube videos to external media. It doesn't gets hang, its smooth like that of in ios and android. one of the best thing i like is we can also stream audio only.

YouTube. Watch, cast and Chromecast and AirPlay. Use TubeCast as an incredible YouTube client and cast YouTube videos on your Smart TV, Chromecast, AirPlay, Google TV, Roku, Amazon Fire TV, DLNA, Internet box, Xbox One & 360, PS4 & 3...

 Features : 
1 4k(2160p) QHD(1440p) Full HD (1080p) SD (480p) 60fps
2 Download YouTube videos (Pause and Resume)
3 Play the sound of the video under lock
4 Login to your YouTube account and use all the features (subscribe, watch later, history, my videos, subscribers...)
5 Video 360

Complete Cast features : 
1 Cast video or audio on your Smart TV (Samsung, Philips, LG, Sony, Panasonic, Sharp, Toshiba etc.)
2 Cast online and downloaded YouTube videos (WP8 only)
3 Chromecast (total control Volume and seek)
4 Airplay Apple TV (total control Volume and seek)
5 DLNA (total control Volume and seek)







Screenshots of my phone playing audio only : Left

playing HD video "i love Nepal" : Right



Windows Phone Store Link :
https://www.microsoft.com/en-us/store/apps/tubecast-for-youtube/9wzdncrdx3fs