Nope, that's not normal. Do dead trees look like this even when not snow-covered?
at this moment I can't answer to this, 'cause my location is pretty cold in winter and snowstorms are very common
I'll load another world and find a warmer location to check this
have FUN with the multitile trees (actually I didn't even get how they will look like, and having a tree tall as a mountain doesn't sound very realistic -_- but we'll see in the released version how they will look like)