While the TF2 community has come to accept that the official class role system has almost no basis in reality, Overwatch rolled out a very well-defined classification system that mostly makes sense. Tanky characters are tanks, healing characters are in support, ranged DPS are in offense, and area denial are in Defense.
So many people can’t fathom why Symmetra is in Support. She’s the only support character who doesn’t heal, and her turrets are very obvious area denial. She seems like a slam dunk for the Defense category, and a reclassification would come with an added bonus where players would stop picking her when the character select screen warns “no support heroes!” in the current team consistency. (Update: Blizzard actually fixed this one! The new update changed the warning to “no healers” and excluded Symmetra.)
However, clueless players aside, I’d argue that she fits the Support class far better than the defense class, for two reasons. The lesser reason is that she doles out +25 base health, which is kinda healing, albeit more like a shield, but its a very support-oriented ability. Of course, Torbjorn has a very similar ability, and considering he’s in defense, Symmetra needs to provide more support than that to qualify. And she does, but it requires a different way of looking at her ultimate.
Once she’s built her ultimate up, Symmetra drops a teleporter at a location of her choosing. It comes with 6 charges, and anyone can use it to immediately return to the front lines. Consider that for a second. Just like Mercy, Symmetra is capable of returning fully-healed allies to combat faster than normal, which is absolutely the behavior of a support class. While not “healing” in the traditional sense, it negates the sting of death by almost canceling out the consequences of respawn.
Obviously she still plays a lot like a Defense character when her teleporter is up (or she’s building ult to put it up) but one of the interesting things about the Support cast in Overwatch is that each fits into a different tree on a design level. Zenyatta plays like a DPS class with his orbs, Lucio plays like a tank due to his insane self-healing, Ana is a Sniper, and Symmetra is a builder. Mercy I guess is the most “pure” Support class, being the first and the baseline the others are all compared to. But I absolutely think Symmetra still fits into the Support classification, even if she’s the only one who doesn’t heal. Thanks to Mercy, “bringing teammates back from the dead” is a support ability, and Symmetra’s teleporter does that in its own way.