Heya! I used to main Orisa in competitive for a period of months. Although I’ve been retired from the scene for almost a year now, I think I still have one or two tips to throw down which are still valid. I agree with a lot of what LftClickHero has to say, although I’d like to expand on a couple of his points a little bit.
Firstly, when it comes to Orisa’s aim, treat it like an artillery / suppression weapon. You can absolutely be accurate with it, but you have to couple it with tactical uses of HALT to guarantee reasonable damage. Here’s the maxim I used to play Orisa by:
Go for the Low Hanging Fruit
Orisa’s weapon has vast capacity and huge damage potential, but most of it is wasted if you try to shoot for difficult targets - if you have a choice between a slippery DPS running around your team, or a gigantic enemy tank barrelling towards them (hello Reinhardt!) shoot the big guy first. You want to maximise the potential of your weapon, and you can only do that if your shots are going into enemy bodies. For example, if you’re going to start shooting at Mercy, it should only be because you’re certain of closing the kill. If you’re in any doubt, don’t bother.
The same philosophy applies to HALT. Sure, you can use it on big clusters of enemies to help your team ulti into them - but most of the time you should be using it to bully and harass squishy targets and set them up for easy shots by you or by your teammates. With HALT, you can prevent retreating foes from completing their risky getaway, and since you only have one target to go for, landing the orb shouldn’t be so hard.
When it comes to Fortify, use it as your last resort to block incoming burst damage - it’s best used to block stuns like McCree’s flashbang or a Reinhardt charge, but it can also save you from a Tracer’s onslaught in a pinch - once it’s gone though, it’s gone, and you won’t be getting it back for a considerable amount of time. If you know you’re going to need to use it, the right time to pop it is just before you’re about to take a huge chunk of damage - anticipate it before it happens - ideally so you can hit shift while you still have plenty of Armour left in your health pool. This will stack up the damage reductions so you can shrug off otherwise-fatal blows and squeeze the absolute most mileage out of your fairly modest health pool.
I hope these tips help you!
[EDIT: One last thing - HALT lines can be deceptive because Favour The Shooter doesn’t work for them - you simply have to develop a feeling for when the right time to pop is - do it more by rhythm than by sight
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