Probably already asked, but couldn't find it, so sorry if it's already answered and then close this thread
I'm not sure about damage output as I'm not using damage meters in Beta, but after doing some testing on my own and watching the numbers, I think that Grimoire of Service is behind the other two. A 20 sec Dps "boost" by summoning another demon that doesn't really deal much damage can't compete with a flat 20% damage increase on pets or a 60%->30% single target damage increase for 15min.
I wanted to use Service because I don't like much the Supremacy demons but the Fel Imp, but I do like to have my pet for damage and utility so I don't want to use Sacrifice, but now I'm kind of "forced" to use one of them.
So... Are the three grimoires (more or less) balanced between them damage wise? Or is there an obvious choice?