You may not realize it, but you're kind of being one-sided/biased in your argument.

Originally Posted by
Khamsin
Relic weapons don't let you do anything new aside from continuing light/dark, which does little to change the strategy of a fight or open new avenues.
Using the exact same approach I could say "Relic Horn doesn't let you do anything knew other than give a higher MP regen."
In reality relic horn really doesn't change the fight much at all. If you lose to Ouryu big time without a Horn, odds are you'll lose big time again even with one. Depending on the PT the BRD is in all it will really do is give them slightly more MP over time... In most cases the MP will go to BLMs, which translates into more damage to an extent (pulling hate = death or log), which is no different from the function most other relic weapons serve.
Or I could also say "Aegis doesn't let you do anything knew other than utilize PLD/WAR without hurting the alliance as much."
But, what's so great about using a PLD/WAR over a PLD/NIN? Even if the PLD/WAR has Aegis? Nothing really I can think of, I'm pretty certain a PLD/NIN will still take less damage (thus generating more hate) and be more tank PT friendly since they rely more on Curing than a PLD/WAR does.
I've also yet to see a PLD/WAR generate as much hate as a PLD/NIN in any major HNM fights, and while experience with those jobs and their performances in certain linkshells vary from place to place, I'm pretty certain this is generally accepted now.
Seriously though, all your examples are way too extreme. Odds are that if you wiped to Tiamat at 20%, you'd wipe even if you had a Horn or Aegis. Horn/Aegis doesn't suddenly make your LS invincible, it takes a lot more than that, and you don't need either of them to play at the top of the game.