...fail

By design, Sona is a support and that's why no matter what you build, there will always be a supportish feel to Sona, however building her strait support, in my opinion, is not the best course of action anymore as her utility got increasingly buffed while her supportive nature is consistently being nurfed. The reason I roll with 9/0/21 masteries no matter which build I use is because it is the most versatile mastery setup that can be used by both tanks, carries and supports therefore allowing you to freely flow between different builds mid game without having the masteries being incompatible. The reason for the choice in CV and Flash are mainly to bluff your opponents into attacking you. As for runes, I have listed a few other possible runes that you can use if you feel that CDR/lvl is not to your tastes. A general rune page such as mpen/arpen reds, mp5/armor yellows, cdr/mr blues and hp/movespeed/gold per 5 quints are also acceptable.

I..........I'm...I'm lost for words, honestly.

Sona used to be the one of the best (if not the best) support in game, then Riot nerfed her heal because they didn't like the fact the high amount of sustain that was added to the bottom lane by the supports and instead of questioning her viability you build her tank, offtank or even as an AD carry?
You think Sona is a better AD carry, tank or offtank than a support? You build AD carry items but still take 9/0/21 masteries with Clairvoyance and Flash as summoner spells and take CDR/lvl Quintessences? None of this makes sense xD

I'm not downvoting and to be honest I don't know why I'm not... But this..this is weird, it really is