I think you will be fine if you are searching actively as cave specc shaman. Just announcing the standard "shaman lfg" will in most of the cases lead to a group beeing really unhappy with your specc because they need specc buffs. The specc in itself is fine, as Runental pointed out, but oftentimes people expect something different.
A few things I want to point out:
Shadanwolf wrote: ,,,dots that kill and interrupt.....
Not entirely correct, the dot rupts when it hits, as ist he case with most casts. The ticks of the dot do not rupt.
Shadanwolf wrote: area disease that reduces healing by 50% for 3 minutes
This is correct for people running solo/smallmen. Supporters can cure disease, so you have to reapply disease frequently. And aoe disease a base line spell, so every shaman can do this. Yes, cave shamy has a higher pbaoe disease, but it has the same effect as the lowest, except for the resist rate and the duration (2/2.30/3). Most shamans have cave as a side specc, so an aug specc shamy has acces to the same spell, just a bit more difficult to apply.
Shadanwolf wrote: How does a single target mele compete with such a force multiplier ?
He doesn't. A melee is there to burst down a single target together with other dps classes. Cave shaman has no real burst dps but several aoes. Completely different role.
As I said, communicate that you are cave specc when searching for a group, but expect to not be picked instantly, as you play a niche spec which forces a group to run two shamans.