I've got roughly comparable gear sets workable in T4 for both Enhancement and Elemental, and I don't find either of them to be particularly spikey. The only thing you really have to watch out for is jumping the gun on your DPS before your tank has enough time to establish threat, but you should be doing that anyways and it isn't really in any way specific to the Shaman class.
As for out-DPS-ing people in T4 gear when you're in 67-70 blues when you're Elemental... it's completely possible but it doesn't mean that it should be happening either. You can crank out some really impressive DPS by the time you at least get your welfare PvP epics on (I could, at times, hit 900 DPS in mostly S1 and Kara-prep blues), but most classes in full T4 PvE gear should still be doing more damage than you. If they're not, that's more on them failing than on your awesomeness or that of your spec.