Would it be interesting and also thematically logical for Ruby in Helm slot to give you Armor % like Amethyst gives you Life %, also matches with paragon defensive stats, instead of the basically useless XP gain stat.
XP% gain is 100% reduced in greater rifts, besides that, Ruby gem XP Gain is 10x weaker at lvl 70, and you can only potentially boost the Ruby gem XP value to 41-82% (latter with a legendary) and that works only from lvl 1 to 69.
Like before few weeks before the Topaz was changed I suggested changing the Magic Find into Resource Cost Reduction, but I prolly wasn’t the first one to think of that.