Crit Damage Runes

Okay so I decided I was going to see how crit damage runes played for Tryndamere jungle. So what I noticed after about 3 games and going into the practice tool is that they don't actually work. The is actually no increase in damage at all. I don't think I'm wrong on this I checked it multiple times. Occasionally there appeared to be a sligt increase and when I say slight I mean maybe a ten damage difference. For the record I was running the quints and marks that give increased crit damage. Based on my experience they don't work at all. If you need screenshots I'll send them but this is pretty easy to check.