Measuring the comparative effectiveness by noting how much more times the hero costs over the base troop is completely irrelevant and demonstrates already that you aren't clear on how costing should work. This kind of comparison is being made in a vacuum, so to speak, and does not take into account how things actually work out when points are being paid to create a new army. It's being used solely to try and win an argument by using irrelevant mathematics.
It's easiest if I illustrate with a negative example.
Let's start with your calculations that a Bruiser only costs 2.1 times more than a Maneater, for basically an improvement in damage mitigation and almost no improvement in damage output.
Let's then take a Saurus, who has very similar WS, S, T and I, weighing in at 12 points, coming on a 25mm base.
By your measurements, for a Saurus hero to 'match' a Bruiser in terms of efficiency, he'd have to cost around 26 points (12 x 2.1) and get, let's say, the exact same improvements over a Saurus that a Bruiser gets over an Ogre: 2 WS, 1 S, 1 T and 1 I - making him WS5, S5, T5, I2.
Does that really look like a reasonable statline for a 26 point model? For 104 points (almost the same as a naked Bruiser), I could field 4 of these guys taking up the front rank, filling it with 8 T5 wounds, 16 S5 attacks. That's double the wounds and 4 times the attacks of a Bruiser, at the same S and T.
Do you see why your comparison is utterly ridiculous now? In no way has your entire post shown that Bruisers are the most cost effective combat characters in the game.
You can get an idea of cost-effectiveness by comparing what you
gain from paying the
cost differential over the base troop.
Take again the example of the Saurus, because it's the closest in terms of many stats. For 85 points you get a Saurus hero, which is a 73 points upgrade - very close to the cost of a Bruiser upgrade over an Ogre (75 points.) For that amount of points, you get very similar gains: 2 WS, 1 S, 1 T, 1W. It's close, but suddenly, looking closer, you realise you got shortchanged 1 I and 1 A.
Even that, however, is insufficient. You have to also look at what you actually get for your points, ie: what the final cost (not relative) and statlines are. Being that WS, S, T, I and Ld are the same in the case of Bruiser vs Scar-Veteran, the remaining relevant stats are M, W and A. The Bruiser has a clear advantage in M, obviously, and some advantage in W, getting 4 for 105 points against 2 for 85 (keep in mind the Scar-Veteran has 1 better 'pip' of armor however, which makes it more even than it looks.) However, in terms of attacks, where the number of attacks per unit 'frontage' is relevant, the Bruiser is terribly behind. You get 4 A over 40mm, while the Scar-Veteran is making the same 4A over 25mm.
Looking at it in practical terms, fielding 3 Bruisers in the front rank costs 315 points before equipment, and yields 12 W and 12 A. Fielding 5 Scar-Veterans costs significantly more, 425 points, but you get 10 W and 20 A. It's close - but certainly not far apart as if you were to make the random comparison of cost relative to base troop cost. Bruisers are more cost-efficient with defensive Magic Items (armor and ward saves), having more W, and more survivable individually, which makes them marginally more cost-efficient with other Magic Items as well. Scar-Veterans are definitely more efficient when it comes to Magic 'buffs', however, with their greater number of A for the same cost and frontage. Whatever the case, it's far from clear which is the more cost-effective overall. If anything, it seems to demonstrate that the points balancing seems reasonably good between the two.
Finally, even looking at what you actually get for your points does not complete the cost-effectiveness picture. You still have to compare what you got against what you could've got (opportunity cost), and this is, I think, where the Bruisers really fall short. Our army is so packed full of superior RnF troops now that it's difficult to justify the cost of Bruisers. M6, Ogre-Charge, Stomp, immunity to Stomp, Thunderstomp and Killing Blow sound fantastic, but almost every other unit in our army also has these things. Is the concentration of force gained by fielding a bunch of Bruisers in a unit necessary or effective? In a typical 2000-2500 point game, I'd hazard a 'no.' As this is a long enough post as it is, I won't get into that here - maybe later on
