Having pugged all of those in F2P, here's my opinion
Mw Monk - Druid like mobility and sustain but just... didnt really have the punch I was expecting. Lots of fun though. Im a terrible monk player so someone with an affinity for the class could probably make this work and have a ton of fun.
Ele Shaman - just straight up laughable damage. Decent enough utility kit but if your just gonna drop totem and occasionally heal someone, play a really aggressive resto shaman and be a god.
Rogue - the control is cool in small group situations but rogues are so ele force reliant that without it, it feels like you arent even doing damage. If I was only pugging WSG and made it my goal to be as annoying as possible, I would probably enjoy rogue but it really wasnt for me.
MM Hunter - fucking fantastic. Quality damage output but the CC is really why you're there. Pet slow, conc shot and trap. All on top of a really fun rotation, some good defensive CDs and enough damage to feel useful? MM is probably the one of these four I'd most highly recommend. I've been playing a bit more of it lately and having a blast. Especially when paired with an even somewhat aware healer? Its good stuff.