Or double its ammo capacity.
We can get halfway there with the Extra Ammo Capacity suit mod...
Double damage yes. Projectile velocity, no.
Doubling the Oppressor's current damage of 16.1 MJs pushes it to 32.2 MJ/s. That's still behind the 35.1 MJ/s of a G3 Intimidator, and with the current projectile velocity the Oppressor's
actual effective engagement range is within the Intimidator's effective engagement range - which you can vastly expand with the use of a Scope mod due to the mod's unstated pellet spread tightening effect, with frankly terrifying results. Upping the damage of the Oppressor but not the velocity still means you are competing in shotgun ranges, and with the Intimidator's G5 DPS of 60.1 MJ/s you will lose that engagement the majority of the time.
On top of that, the Tormentor sidearm can achieve a G5 DPS of 38.1 MJ/s, and can down a High CZ target (likely ones that have the same health as a player in a G5 Dominator) in 3 shots minimum (2 body, 1 head). At a rate of fire of 1.7/second, that gives you a minimum of
5.1 1.76 seconds (I can't math lol) to return fire and eliminate your target; no velocity increase means we are operating in the Tormentor's effective range as well. Being a sidearm, the Tormentor has an inherent handling bonus, so your target is much more evasive than you, as well as being able to take advantage of "peek shooting" - taking a shot, ducking behind cover while the next shot chambers, then peeking out again to take another shot - because the Tormentor frontloads the damage into single shots instead of a stream of shots. The Oppressor needs to maintain a steady stream of plasma on a target to kill, and thus will generally lose that engagement. Even in a straight DPS race, the Oppressor will still lose with a twofold damage boost.
In short: doubling the damage won't solve the Oppressor's issues. Changing its projectile velocity, and thus its effective engagement range, will.
(As an aside, the above are textbook Hand Cannon vs. Auto Rifle scenarios frequently seen in Destiny 2's PVP modes. Only way out of those are to outrange the Hand Cannon with a Scout or Sniper Rifle or force a close range shotgun engagement. Due to various factors such as map design, Hand Cannons have been overly dominant in Destiny 2's PVP since the Forsaken expansion released in 2018.)
It's supposed to be slow.
After extensive playtesting, I don't see any particular reason why the Oppressor's projectiles should be slow to the point of being difficult to hit targets with at ten paces away.
Don't like slow? Use the other AR's.
My main weapon at the moment is that G5 AR-50 I posted in the OP.
Don't like the resistance issues? Then complain about that.
The AR-50 is able to chew through targets in a High CZ in less than an Extended magazine with absolute ease, despite unfavorable shield resistances, as shown in the following video:
Source: https://youtu.be/67DQ_etkIAA
High CZ targets are the hardest NPCs you will encounter in Odyssey. If the AR-50 can handle those, it will handle anything Odyssey throws at it.
So no - I actually don't have an issue with the resistances.
I'm sure they'll get right on it! Right after they address the hundred other issues making Odyssey hardly worth spending time on.
Source: https://www.twitch.tv/videos/1052006919?t=0h40m59s
They're definitely thinking about weapon balance alongside other issues. While more pressing issues take priority, they shouldn't preclude these balance discussions... though we should have discussed this back in Phase 2 of the Alpha, but hey - better late than never!
Damned impressive stuff. Was holding out some vain hope for the oppressor, but alas, it shall not be today.
Out of interest, does the greater range upgrade improve a plasma weapon's shot speed, or did you just add it because the default 35m is kinda pitiful for an AR?
Sadly, Greater Range does not increase a weapon's projectile velocity. It does increase the range at which Damage Falloff kicks in. I added it to my first Oppressor in order to figure out what the mod actually does, which I documented over
here. Needless to say I was - and am - disappointed that the mod doesn't help much with the Oppressor.
)
This. Unmodded, all the other Manticore guns have tiny magazines and slow reload. That is the Oppressor's advantage/balance. And when it hits (my technique is to run at the target, firing) it will chew through targets pretty fast, without having to swap weapons. 
