I feel that the nerf was necessary.
In preparation for GST, I went through all EC items, and Arcade items.

I never realized how good the Arcade guns were-- the OPR was easily better than any EC item on the market.
At least, for me.

The only "weakness" it had was the low damage, which in no way really stunted the gun, because of the many advantages it had.

-Moderate Spread
-Knockback/Electricity/Fire
-High Fire Rate
-Low Freeze
-Automatic Reload

The Automatic Reload is definitely the thing that gave it the biggest edge.
People compare it to the flame, but the flamethrower has a lengthy reload to contest the advantages it offers.
The OPR, by contrast, has an automatic reload, which is yet another advantage in its favor.

Even with the nerfed fire rate, the gun still dominates.