For hydras, do Mars patrol and go to valley of the Kings (where you enter the Black Garden portal). A red bar hydra spawns every 1.5 minutes or so. Double it up with weapons as well. I ran it a few times with a Universal Remote / Swordbreaker combo to get shotgun kills while I was farming hydras. Stacking these challenges is the fastest way to rank up grimoire. For ogres, I agree with previous poster that shrine of oryx is best. There is a YouTube video on farming ogres that lays out how to do it. Also remember to swing by the Temple of Crota whenever you are on the moon as well to get the ogre inside.