I feel like it's important to point out again that what some people might think is "sandbagging" might just be guilds that don't make TW compulsory. Last TW in my guild I think we had 42/50 signed up - not because we were sand bagging, but because 8 people were just busy or simply didn't feel like doing TW. We don't punish people for that. TW is simply not appealing for some people and some guilds have a mix of players that may or may not want to engage. Our one rule about TW is, if you're not going to participate, don't sign up. I wouldn't call this sand bagging.
Lets face it - even for people that like TW, it's become pretty stale.