Its nearly 3 years later and the Tortugun still isn't played often. Because of that, i think the changes that we're made wasn't enough (they we're a good start).
My suggestion to see it more often, would be another buff. I like the overall design but playing with it is still micro intens. Because of that i would add a corps leach mechanic (Like the Harvester has it) to it. The range of the Corps leach should bei realy small, maybe 5 m and it shouldn't get the full corps HP (maybe 33%).
That way it is still motivating to devour units to fill the bar fast and to get the DMG or the reduced DMG taken buff. But there is a secound way to fill the bar. To do that the Tortugun needs to move to its target, so you probably won't do that in Fight. But after a battel you can consum the corpses of your enemis to fill the bar a little and move to the next Battle.
Another way to balance it would be to add a debuff after corps leaching (it feels ill after eating the dead bodys) giving it for x secounds a big DMG reduction. That way you would need to make Sure that you don't eat corpses when your are in Fight, making the possitioning important.