I never liked playing soloq in comp and only did that like once out in a whim haha. There's way too many variables in soloq, and OW is actually a game that you cannot reliably solo carry in. There's a lot of things your teammates can actually do to actively screw you up and cock block you. Things like Ult feeding, etc etc.
To actually carry a worse team in soloq you have to be significantly better than the enemy team and over compensate for your own team's error lol. Which is why I played mostly triple queue because 3 is just nice if you want to go 1-1-1 composition to hard carry, though we occasionally run 2-1 tank/dps-support if the team is really really bad. Overcompensating for teammates is quite annoying imo e_e thus I didn't actually play comp that much either, and basically took fights 3v6 cos why not.
Anyway I've been playing Symmetra lately and am quite enjoying her for her kinda lazy playstyle hahaha. I like using her sentries for map awareness and applying the slow effect everywhere and basically slows down pushes. Usually place sentries in 3-3 or 3-2-1 configs. I keep hearing people that Teleport ult is underpowered or whatever, dies too easily etc. But the thing is, Teleport isn't something you should immediately throw down lol. Play Symmetra like Mercy once you have the ult, very passively. The moment you feel a push is coming I just nope and run away lol. Symmetra isn't going to contribute to a fight anyways. The best thing you could do is prepare your sentries to be in a good position before fights happen so that you can net your team a little help.
If people start dying, that's when to decide whether or not to put the tele. If 1-2 person died, can they just walk back in time, or should you tp them. Just assume that once you put your tp down, it's going to go down after that one spawn wave. It's a pseudo-rez and that's how it should be played. If used properly it can be better than Rez because it's safer and allows for repositioning. Basically don't plonk it down the moment you have it lols. Most people know to kill Mercy first in a fight, but fewer know to kill Symmetra if she hasn't placed the tp yet.
I do feel like her kit is a little underwhelming atm, and many people think that she should be a Defense hero which I quite disagree. Her Teleport is a support ult, unlike Ana who has a DPS ult. Sentries slowing enemies, I would see it as half support half defense. It feels like a rooting spell or something lols. Her shield HP thing is really lazy imo and isn't really skill indexed. It's not too hard to keep track on deaths and who still needs shields, though most Syms probably don't even bother with that.
The shield thing should probably be changed. Was thinking of making it a more spammable but weaker version of Zarya's barrier. Apply a temporary shield on a player that resists damage either to a certain amount or over a certain time. Key thing is resist rather than completely block. The thing with healers in OW is that no matter how much healing you're doing, unless you're Ana with heal grenade, there's is no way you can out heal damage done in this game without a Reinhardt shield. Damage per second on each person is roughly ~100/s whereas the average heal on one target is like ~40hps with Zen/Lucio, or ~70hps with Mercy/Lucio. Ana is the only true viable healer that can deal with the amount of burst damage OW has. I feel like if Symmetra can provide actual useful damage resistance, it would indirectly be a buff to all healers such that their heal output can actually be used to keep people alive rather than as a thing to just farm support ults lol. This way she can be a viable second support by complementing heals, and is rather skill indexed at managing resistance and heals.
Rotating heals in this game is really kinda iffy and doesn't feel good or as rewarding as in TF2. Giving Symmetra damage resistance skill is something that I think would help her and the game. There's other things but that's for another post.