With the core goal of 10.3 akali changes - getting her out of the clear dominant position she had in high elo and pro. We're now seeing her significant drop in priority, which will allow us to slowly put power back into her.
I don't see an issue with the system at it's core. It adds some additional tuning for us to do over time - maybe in the future the threshold is a little higher or lower to match the item system. The choices and build variety created outweigh the cost I think.
We looked into this recently and aren't taking any immediate action mostly because swain mid seems stronger (though less popular) than support. If more players want to play him support, we're not currently wanting to stop them.
IMO - feel free to play him mid, he's very much viable