So, I started my Titan playthrough today, and was wondering how close anyone came to maxing out there weapons for the trophy. I finished God and still need about 15k more orbs.  
 
Do you have to find literally every single red orb chest?

 I maxed them out on Titan because I found every Minotaur Horn, Gorgon Eye and Phoenix Feather as soon as I could. Once I did that, every chest further into the game that would have held those items turned into a chest full of red orbs. Finding each of these gave me barley enough to max out.

On my first playthrough on Normal I didn't quite have enough (missed by one level on the Nemesis Whips) and had all upgrades for health and magic, but was missing one minotaur horn. 
 
My second playthrough I used a checklist for the horns, feathers, eyes and honestly by the end of the game I had everything maxed and a ton of red orbs left over. So I guess it really comes down to those extra chests that can contain orbs once you get all the other upgrades.

Its easy if you max out health/magic/items early, even on titan.