For the love of god Riot, stop trying to balance Sona for ARAM and just perma ban her from the mode
The healing nerf she took was to clearly tone down her presence in ARAM The upcoming nerf is to screw AP Sona, something what 99% of people play when they get Sona in ARAM
There is literally 0 reasons to nerf her on SR but many to nerf her on ARAM The only complaints about Sona come from ARAM and new game modes
Stop treating her like Mundo back in 2009 where you had him nerfed because of his presence on Twisted Treeline, we already know this chaotic way of balancing does not work