Which Tier 1 items are you working on?

@SFSeventh I hit Mastery 201 with Boris.   I use Boris auto-turret as an enemy alarm to switch to my sidearm when enemies are close as I play sniper ALOT and thus am scoped in most of the game and can't watch my back or sides very well.  To be honest Boris isn't a very good character over-all as my K/D doubles when I switch to some of the more OP characters.  Thus I only use Boris with sniper and switch to better characters when running anything else.

I'd suggest playing Boris in TDM Hardcore for higher turret kill rate as players die quickly in that mode.  Play Boris in regular TDM for higher damage rates as players run in herds and get lite up by the turret while engaged with other enemies on the smaller maps.  Place turret high and back on ledges so hard to see it but easy for it to see enemies.  Place turret in bushes and near brush so it is blocked from sight on 2-3 sides.  Even place the turret in the shadows as if placed in the sunlight it is easier to see.   Sometimes I even throw smoke to protect the turret from the back or sides.  Treat it like a team mate and keep it alive by picking it up when damaged and replacing with full health immediately, etc...

Also note that the turret works best not only on some game modes, but especially on certain tiny maps like TDM Manifest, most Rush maps when placed near objective up high, etc.  The auto-turret does well on smaller maps with smaller groups of players forced into smaller spaces.  I don't think conquest is a good way to level the turret myself.  Breakthrough can be decent but only a few maps and few locations for the turret...

Dice increased the auto-turret speed, shots fired, etc recently as they nerfed it too far at one point, so it does better in Season 3 than it had in the past...