Is There Any Way to Farm XP During Post-Game Play?

I'm trying to unlock the trophy True Hero - Purchase every positive Karma upgrade for each power on hard difficulty. I've completed all of the story missions and I'm about 8000 XP short for the remaining upgrades.

Is there any reasonable way to grind XP during post-game play so that I can get this trophy without having to play through the game again? Keep in mind that on hard mode your enemies reward you with much less XP.

First of all, remember that in order to gain all good karma powers, you need to choose to do all the good side missions instead of the bad.

If you have a save a few missions before the end boss, I recommend loading it and replaying the last missions, I remember a mission very close to where end boss is located where large groups of enemies were fighting each other. I kept playing the mission, killing the large enemies then killing myself - the XP stayed. It took me a chunk of time but I managed to gain enough XP for the last upgrades.

If you're past that mission, I recommend you collect shards and dead drops, complete side missions, capture zones and perform stunts. If you find these method still don't provide enough XP, try lowering the difficulty in the settings.

Also worth noting, if you downloaded the free DLC power (the blade melee weapon), you don't need to buy it to get the upgrades trophy, so focus on getting the good side powers first.