I went on the PTR to try Sigma a little, didn't really do it. Queues are horrible as a tank, upwards to 10 minutes. I'm not that patient. I did play in No Limits but that was horrible way to test a barrier tank with barriers everywhere.
So I settled on QP and queuing as a healer, first queues were instant which was fun. Obviously there was a Sigma on each team all the time.
First impression as a healer observing and healing him is that he looks fun, but seems undertuned. He felt squishy.
He seems very weak to Winston, he has no escape, takes a lot of damage from Winston primary. In close range both his primary fire and rock thingy do damage to himself. Winston primary bypass barriers, and are not absorbed by his grasp thing. I think he's going to be very weak to dive.
He loses all barrier battles, his barrier works like Rein where it needs to recharge but has less health. Orissa's barrier gets to full health every time it is deployed but isn't as mobile.
So I am not sure where he will fit. He can't dive, and is weak to dive, and can't win barrier battles.
The one thing I did notice as a healer, is that players were rarely above 500-600 health with him so their use of grasp wasn't great, or it is too hard to use it properly. I'm wondering if a good player would be able to keep himself at 600-800 health with decent uptime with great use of his grasp ability. That might change how squishy he feels.
I think this might be a spot where they have a lot of knobs to use to tweak him. Change the size of grasp hitbox so it's easier to use, change the duration so you have longer to absorb damage, change the cooldown, change the ratio of damage to shield so you can more easily get it to 700-800 range, change how fast it decays etc...
While his barrier is a bit on the weaker, it's very versatile. I think we'll see some cool play with it. In one game where we had an Orissa and a Sigma, he left his barrier on high ground in front of our widow who was safe to snipe for a bit while he moved with the rest of the group behind Orissa's barrier. Not saying it's a great play, but it was interesting to see. I think it has potential.
His ultimate is hard to pull off, like Doomfist it is somewhat easy to get out of it's aoe. It can be devastating if used properly though. I think it will combo with a lot of stuff, McCree, Soldier's ultimates, or even just McCree, Soldier, Widow shooting at totally exposed targets. D'va, Zarya, Hammond.
That said, it will take a while to truly see how he'll impact the game. Right now, I see him being used less than Rein and Orissa in the MT role which is what he's supposed to be.
On a totally different note, with the disclaimer that this is the PTR, but I love role queue so far. Almost all the games have been great fun. Having guaranteed 2-2-2 on both side almost makes all games balanced. It's not perfect you can get a Roadhog/D'va combo being healed by a Zen/Lucio...but that is still better than having a D'va with Zen and 4 DPS.
If live games were a on scale of 0-10, I'd say PTR 2-2-2 is maybe a 3/4 to 10. It just raise the floor in terms on quality. I'm looking forward to it on live if the quality of games is similar to what I got on the PTR.