I believe I found a way to balance Sterak's Gage to make it less of a "must buy" on Marksmen

I believe that the best way to do that is give it Atma's Impaler old passive and take away the bonus AD you get when the shield activates. For all of the newer League players Atma's Implaler was an odd item to say the least, this is what it was like when it was in the game.

Stats: +45 armor +15% critical strike chance Passive UNIQUE: You gain attack damage equal to 1.5% of your maximum health. Item cost: 2300g (780g)

I believe if Sterak's AD was based off of health that could fix the problem of it being an almost must buy on most Marksman and making it better on Bruisers, which was the original role that it was meant for, and by taking away the bonus AD during the shield it wouldn't be out of control because you would be getting much more AD over time from this Sterak's Gage then the original ever gave. Basically with Atma's scaling it meant 1000 health = 15 AD since bruisers generally build around 3000+ health that would mean this new Sterak's would be giving around 45+ AD which I believe is very good for the build path and would not need the bonus AD you get from the shield.

This is what I believe the new Sterak's Gage would look like in terms of stats and a new build path/the original build path: + + 1100 Gold = Sterak's Gage Stats: 500 health Passive UNIQUE: You gain attack damage equal to 1.5% of your maximum health. Passive UNIQUE: Grants STERAK'S FURY upon taking 400 - 1800 (based on level) damage within 5 seconds (45 second cooldown). STERAK'S FURY UNIQUE: Grants increased size, and a rapidly decaying shield based of 30% maximum health for 3 seconds