I don't think anyone can answer this question yet. We won't know if Shaman will be able to do heroics until a month or two into Wotlk. I strongly believe that they will be fine. We might have to concern ourselves about gearing out a little more before doing these heroics but in the end I think 5 shaman will be able too.

Ramparts? Do I just suck 5 boxing?

That thread is about a 4 shaman 1 paladin team that was having problems with ramparts also. I don't think you can just waltz into an instance and expect to destroy it even if you are a traditional team. You have to take time to learn the pulls and try different things out. Once you get this stuff down and run the dungeon over and over it becomes easy. I know some of the instances that I do I started out wiping alot on trash and stupid stuff.

As far as pvp gear goes I don't think it is necessary. If you look at my armory I have one piece of PVP gear (S2 helm). The reason that people go this route is that it is fairly simple (albeit time consuming) way to gear out all of your team at once. There is a starter pvp set that you can get without doing any pvp once you ding 70 (http://www.wowhead.com/?itemset=746).

I think if you like the playstyle of 5 shaman continue on with it.