To be honest, the Belt of the Royal Deadfire Cannoneer makes the game substantially easier. You can get it quite easily fully unlocked by Act I, and Torrent of Flame obliterates enemies (having a +15 acc bonus), Flame Shield is potent Retaliation (+10 acc bonus), and Firebrand is very strong so long as you have even half good accuracy. The Phantoms at Caed Nua are now a doddle, as if you slap on Rymyrgand's Mantle the Flame Shield will take them out easily enough - even if you are completely stun-locked.
Busting out Torrent of Flame on my Rogue right now, I usually get in the range of 80-120 damage on each target. If you pair this with the Adra Beetle's shock AoE, you can readily nuke a tricky group of enemies regardless of your class.
I'm not in anyway suggesting the Belt be changed, honestly it just serves to make Act I less tedious and as it quickly becomes less and less powerful in Act II and subsequent Acts (if they were going to nerf it, I would recommend they just set the requirements higher than change the actual benefits it gives). However, it's a little weird that Obsidian would completely nerf the pirtate uniforms let allow the belt to remain untouched, as +9/+9 has made them largely irrelevant now.