I'm maxing Str and using Cha trance from Pally, which works fine while Raging. I think you can even use the DL Cha trance while raging (based on the Wiki) but I haven't tested. Having a trance is a lot of ~cheap stats, it's hard to give up on any endgame DPS build (even that build with a mediocre 60 Cha is +12 damage).
Given 0.5 stat-to-damage vs 2.0 stat-to-damage (SWF w/OV), the damage breakeven is 4 Cha per 1 Str. If you're THF it's 5 Cha per 1 Str. The math for that bit is pretty easy
There's some slight differences with stuff like attack bonus and tactics, but damage was your original goal. It's almost always easier to get +1 Str vs another +4 Cha, so you kinda just max Str and then get whatever Cha you can.
Rage is not always better than Str trance. If you had more Str or less Cha, using Str trance would be better for my build. It's pretty close for mine, FWIW. If I scroll Tenser's, have the improved Scream from a party member, have Bard songs, and use a Titan's Grip clicky they break even on my build (let alone Bloodrage, Madstone, Roc's Strength, etc). If I was doing a Falchion build on a non-WElf, I'd be doing that probably (since I wouldn't want to sink that many points into KotC then, which I am since I'm using a longsword).
Cha-max and using rage to fill out some Str for tactics is ok, but doesn't seem super great? Make a build maybe.
In my experience, to have endgame GCS on a DPS melee build is very high opportunity cost. I did it with an 18/2 Pally/Cleric build last year or so, had viable Crusade, GCS, and Turn Undead endgame. But I had full Cha & spell DC filigree, spell DC's from ED's/feats etc, and the gear tetris was a nightmare.
For leveling it's incredible on any Int/Wis/Cha-max toon, but I haven't had much success at endgame on non-casters.
Perhaps to bump your Stunning Blow DC's or something, but yeah I agree. I'm running Str-max w/Rage with Cha secondary for trance (and saves and LoH).