Supports Carry in the New Meta?

We've all played support at one time or another in our league careers, but most support champions take a while to build into carries. I just had a match as Soraka which I more-or-less was the only one on my team to have measurable success

In my short time with league, I've grown fond of Soraka and Morgana, so I tend to play them a little more often than my other champions. No big deal, I support my team, identify targets, and do my best not to get ganked. In some games, I do very poorly. In most, I carry my weight. Shen was a bit weird to play, but looks like I'm not the only who noticed; he's getting TLC from Riot soon.

Anyways, I've had a couple games where my performance was mediocre, yet the best in my team. Case in point, last game, we were steamrolled by Sona, Veigar, and Heimerdinger. Initially I wrote it off as those particular champions being pretty OP on their own. After a couple failed surrender votes, and the game ending, I was shocked; I was the only one on my team with positive kda, decent-ish (read mediocre) CS, and gold. My opponents weren't really OP; they'd taken a huge advantage in gold. I'm getting much better at last-hitting (to the point where I'm often one of the wealthier players), but I'm still not used to some of my champion's damage output.

My first question is, "What I should be doing in these scenarios, when my team lacks the skill necessary to keep up with the opposing team?"

Secondly, reviewing the deaths, should I have left top alone to help Caitlin who was having trouble pushing Veigar?

Finally, what can be done to ensure I keep improving?