I found the plans for the ruby and made two of them in the PTR for my manticore. I had ~177K paper sheet damge with two emeralds in sockets. When i switched to the ruby's i gained ~17K paper sheet damage.I did not see a huge drop in crit damage numbers, but i did see that i was killing mops way faster for para leveling. Usually it takes me two hit with elemental arrow to kill monsters at MP1, but with the two ruby's I can easily one shot almost any monster.

My gear is not centered around attack speed, so i am assuming that with more attack speed the greater the benefit would be with these gems. I also noticed that I gained more damage from two ruby's compared to one ruby and one emerald.

I know that gear is really the key factor in making one gem better than the other, but with the gear I have on now, it made my damage go up.