So unless you're living under a rock, you might have noticed that Sona + Taric bot lane is a thing at the moment, and it works pretty well do to all the sustain and utility those 2 champions bring.
Unfortunately, this strategy is a pretty bland and non-interactive one, so it'll likely need some adjusting: however, I don't think it's appropriate to nerf either of the 2 champions, since when played by themselves in the support role, they don't seem to be overpowered.
The real issue is that this is essentially another take on the funneling strategy, but instead of funneling gold from both jungle and mid-lane on a scaling damage champion, you're funneling gold from bot-lane and support onto a scaling enchanter (Sona).
The solution then should be similar to that of the other funneling strategy solution - limit the gold income. Currently I think the best way to do this would be to have the upgraded sight-stone / gold-income item also have the effect where a cooldown is applied to the "Tribute" passive whenever you kill a minion. This would prevent supports from getting gold from multiple streams, eliminating the Sona + Taric funneling strategy.