The Problem with Red Mage . . .

[Neisan_Quetz]

Ephemeron is a terrible offhand. This does not change based on what main hand you use.

Excal loses the +attack and hidden effect in offhand. Regardless of whether you use Excal or Almace in main hand, Str Shikargar is still your best offhand in most situations.

The difference between 90 Almace and 95 Excal is not as large as you are making it out to be (adding in new Vara Brigande, I have them pretty much even /nin on DC, and Excal 2-5% ahead /dnc). If both are 99 they're pretty close with my sets (Zelus/Kudzu/PhosNQ). If using Vara Brigande for TP Excal pulls ahead by a small amount.

If you're talking about Dynamis farming, then excal pulls ahead since you can't keep up AM, but I don't farm on Rdm in the first place.