Mage supports fall behind too easily

I find, as a main support player, that recently the meta has shifted to the use of tanky supports, with the newer ADCs becoming stronger. I find that as a result, mage supports such as Janna and Nami have become very difficult to match if the opposing player's support is a Blitzcrank or a Thresh. Not only that, but once you fall behind, there is no way to catch up because your champ is too weak to poke forward, and staying behind means less experience.

Fortunately, in games where I do not fall behind early, I generally gather about 10-15 assists in the latter stages of the game. However if I should ever fall behind more than 1 level from the opposing pair, bot starts to really slide and ganks don't work too well against tankier supports.

What I am asking is does anyone agree that the viability of mage supports has fallen a shade? And if so, what changes do you think should be made? I personally would suggest an early game item that gives 15~ ability power and 5% cooldown reduction (cost ~400 gold)