Number sharing time! As a single archetype, Undertaker Hunter was about 25% of the meta at one point. For perspective, the most popular archetype of Shaman is currently less than half that. Class win rate wise the highest overall number I've ever seen was Druid around 57%. The highest single player in Legend win rate (min 50-70 games single deck) was around 75%, it's usually about 70.
[The win-rate of Undertaker Hunter was] 55-57% if I remember correctly.
The intention wasn't really to prove any point, but just to give perspective on Undertaker Hunter popularity for people playing on ladder now. However, all of Shaman (every Shaman deck) right now sits around 19-20% of games, which is still around 5% less than the Undertaker Hunter solo archetype was.