I don't know the exact buffs currently, but I know the last time I checked one of the buffs was an increase to the heal and shield power, so please correct if I'm wrong here...
..but why not just revert the shield nerf they did a few months ago? And give Sona her heal back, or at least increase it a bit? And if Raka's w isn't doing enough, which it's actually a slightly strong heal as is, increase that heal a little?
If supports are so screwed after being nerfed both in items AND their own stats... maybe give them some of their stats back before changing the items? Most supports were actually in a perfectly fine spot, but then got nerfed/gutted. Either because the heal was too strong(Sona), or the shield prevented the enemy from winning their lane right off the bat(Every support hit by the shield nerf). Not to mention they got nerfed in gold income by taking away their, what? 1 gold per minion death near them?
We honestly need to stop changing items, and start changing actual champion stats the way they need to be changed.