Sorry, but proxy Singed is not healthy to the game at all.
First off, you're taking CS away from other laners, this means experience, and gold that the enemy now has more of, over your teammate.
Secondly, almost every proxy Singed that I know ends up giving a few kills to the enemy cause they aren't good enough to execute themselves or get away in time, even the best Singed players and mains in Diamonds give up kills which furthermore places the enemy ahead.
Don't forget it's solo que and Singed isn't that popular, and no one thinks of pushing turrets or taking objectives while you distract their team.
Also, with all that gold, Singed is still weak, and literally does no damage more often than not, and his CC potential isn't even that good to make up for the fact of him having all that wasted gold that could have been more useful to the mid laner and ADC if he was triple proxy.
Also, how is Singed fun? You just run around, and farm. Nothing fun about that. The idea of fun is someone like Ekko, Yasuo, Kled, Zac, and many more with outplay potential, but maybe I'm just being too nick picky at this point, but to me, Singed isn't fun to play at all, it's almost as worse as Nasus.
So if I see a proxy Singed on my team, after the game, there is going to be a complaint filed more than likely against him from me, especially if he's intentionally feeding and assisting the enemy team by trying to triple proxy cause that's what he's doing. He's empowering the other team over his team, denying them of CS, letting the enemy team get ahead in CS, experience and gold.
I do not have a problem with lane Singed, but even then, it just isn't a fun pick, and not useful. Sorry to break it to you.
Hope ya have a good day tho :)