Here is a couple of tips for Sigma:
- Your shield should be mainly used to block enemy abilities such as Sleep, Anti Nade, Hook. You can and still should use it to shield your team against heavy damage and snipers as well as rotations.
- NEVER let your shield break, it will lengthen the time it takes to regenerate by around 3-4 seconds, which is a LOT. So always recall it whenever you get the chance so it can always be ready to redeploy when you need it. Even a 5HP shield is enough to block any cooldown, even 1 Shot of McCree’s high noon
- Your succ should be used to absorb enemy cooldowns, ESPECIALLY abilities that generat a lot of ult charge like Rein’s firestrike. You can also use it whenever your shield will be hit with very heavy fire, to gain some extra health + preserve shield HP
But as others have said, I would highly recommend you play him and watch gameplay of better players, and then get a VOD Review so you can get helped with your weaknesses on him.
I personally like to play Sigma and would definitely be up to help with a VOD Review if you can get the VOD recorded =]