I feel your pain infact I knew it was coming even at the start of the expansion. I healed a few of the first bosses in Vaults with no problem but I knew that it would become impossible to keep up with other healers. I was forced to switch to a new class or go elemental which I hated. I went ele and raided for a few months and got sick of it. I honestly suggest you try to do some resto PvP its pretty broken atm. I can't be 1v1 and most of the time I survive 2 even 3 people on me and escape. Shamans have been lack luster healers since the start of cataclysm. Again like you said our major heals are all situation based. The problem I have is resto shamans have never been effective at 10 man and 25 mans it was only a matter of time.
I suggest you take a break like I did back in december. I came back recently and all I have done is PvP which is pretty damn fun. Even thinking of rolling a lock to pew pew in it. Best of luck.