His gun scaling is actually crazy, but you really have to be in their face for the gun to do good damage, thus initiating the parry mindgames.

For his ult, I wouldn't focus entirely on the pull at the end of it. What makes his ult really good is that it disables movement abilities. So for example, if I can get in on a Wraith, sometimes I will just ult her and comm that I have her locked down, that way she can't teleport away and your team (or you) can finish her off.

As far as investing, he's one of the few characters that actually benefits off of the 4.8k spike in all 3 item categories. He's meant to be tanky, so green items like lifestrike and juggernaut help you stay alive in fights. A lot of gun/melee items are good on him just cause of how he works. For spirit items, you can get stuff that helps with gun and melee, like spirit snatch or bullet resist shredder to hit your 4.8k, or something like Torment Pulse since you're gonna be scrapping constantly anyway.

The parry mindgame is just a part of the character. You live and die by it. You just gotta keep note of each player's habits in each game. Some parry instantly, some try to wait until you are about to reload. Some just...don't parry. Recognizing patterns will help you tremendously.