These forums are not the place to ask questions about a shaman. If you haven't noticed, 95% of posts relating to shaman druids and questions or guides about them, have been deleted and banned.
I have absolutely no problems killing any "Melee class with leech" or "pally/barb/shapeshiftR ww asn"s. The naysayers are all people who have neither seen nor built one, so I'd more advise you to ask questions of the people who have.
I personally have a shaman on east, level 91 named Pedobear, if you ever see me in dueling games.
The main thing to note is; shamans have a very steep learning curve. The dueling style is radically different from other pvp chars, with unorthodox strategies like the bear-drivebys and volcano/bear combo hit. To newcomers, it proves incredibly difficult to master; I once let a friend of mine use my shaman, and he managed to lose 0-5 to a tal's lightning sorc that I had been killing in 1 hit. Its not a case of getting the top-end gear, but rather of learning to use it.
Things that destroy shamans:
Leech
Good FHR
Teleport
Access to dwarf, rising sun or hotspurs
Blocking
Thats incredibly naive. The only time anyone can leech off my bear is any time they would otherwise have hit me with an attack. If people could hit me with attacks that easily, I'd be dead. People don't leech off my bear. Its that simple. Nextly, FHR is not too important to the shamans target, nor FBR. Provided they have over ~3k HP, theres no way a volcano is going to put them into FHR anyway. The point is, blocking actually works AGAINST the target of a volcano. As soon as I volcano someone with 75% blocking, they are instantly thrown into blocking animation, interrupting their teleport. Furthermore, since you can only block once every 10 frames, it gives my bear an instant and free hit on them.
Again, the only people arguing AGAINST shamans, are people who have neither played nor seen one. Don't listen to them.
Shamans have low damage, timered and hard to aim spells. All they really have going for them is a bear, which rocks. Basicly shamans give up the higher damage of a pure summon build for crappy spells.
You're very naive. Again, I have an open challenge to ANY dueler on east, even your favored pure summoners. People like you say "zomg, your build doesnt work" on a forum, but ingame I'm slaughtering people left and right. How am I supposed to react to that?