The Chosen might not make their points back, but they almost never give them up, which in a properly built list is just as good, because other units will do the killing.
Going back to our example - yes, you want the ability to put a couple of extra cheap casualties on the Savage Orcs before you get smashed off the board - the extra guys you'll have to swing with in the second round (less than in the first round, because Choppas will have worn off) for taking Flails will still do less damage than the ones with Great Weapons. You basically take the entire "fat" rank off, then you can crash another unit in there to mop those Orcs up. The reason you bring 50 (sometimes even 60) guys in a block is because Marauders usually take heavy casualties no matter what they're fighting, and you want them to be combat-worthy after they mop up their first block, provided that they win.
Warriors you can send against Big 'Uns because they strike first. 2 squads of 18 Khorne Halberd Warriors fielded 6-wide clock in at approximately the same price as those Savages, put out almost the same amount of attacks as they do if you combo-charge them in there (51 for the Orcs with 3 ranks v. 48 for the Warriors), and (importantly) strike before them and hit on a better value. Those 2 squads actually beat those Savage Orcs, as demonstrated below:
2 x 18 Chaos Warriors, Halberds, Mark of Khorne, Musician, Standard-Bearer v. 39 Savage Orc Big 'Uns, Full Command, AHWs + Savage Orc Great Shaman, Fencer's Blades, Lucky Shrunken Head
Chaos Warriors go first. 48 attacks, hitting on 3s, wounding on 3s, allowing a 5+ Ward save.
Math: (48)*(2/3)*(2/3)*(2/3) = 14.22 Wounds
The Orcs lost the whole 4th rank and a bit of the third, so their output is a bit diminished. 47 attacks, hitting on 4s, wounding on 3s, allowing a 6+ save.
Math: (47)*(1/2)*(2/3)*(5/6) = 13.05 Wounds
Bear in mind that these Wounds are split between the two units, so it'll be 6.525 Wounds apiece, which is enough to take out their "fat" rank, but not deny the rank bonus for the second rank on either unit. The Savage Orcs have 1 more rank, but that cancels out with the Chaos Warriors' charge bonus. They win that round, strip the Frenzy from the Savages, and they also lose the Choppas bonus. Next round, the Chaos Warriors win handily, because they'll damage the unit badly enough to not care overly much about the return attacks, as demonstrated below:
11 + 12 Chaos Warriors, Halberds, Mark of Khorne, Musician, Standard-Bearer v. 25 Savage Orc Big 'Uns, Full Command, AHWs + Savage Orc Great Shaman, Fencer's Blades, Lucky Shrunken Head (no Frenzy, no Choppas)
Chaos Warriors go first. 47 attacks, hitting on 3s, wounding on 3s, allowing a 5+ Ward save.
Math: (47)*(2/3)*(2/3)*(2/3) = 13.92 Wounds
The Orcs have lost most of the guys not in the front rank, so their attack output is reduced to 34 attacks, hitting on 4s, wounding on 4s, allowing a 5+ armor save.
Math: (34)*(1/2)*(1/2)*(2/3) = 5.67 Wounds
The Orcs have trimmed the rank bonuses from the Warriors, but they've lost them as well. They're going to be running, and the fight is over.
And while Savage Big 'Uns can be baited, that doesn't mean it's easy. You can build an O&G army around the Savages, and a host of units to clear any chaff that could be used for baiting them. Fanatics, Mangler Squigs, Trolls, Wolf Riders, Wolf Chariots, and Doom Diver Catapults are all useful for this purpose. I play both of these armies, and believe me when I say it's not much of an issue.