I got the fel imp grimoire on my first ever time rift. Done probably 30 since then and still no felhound grimoire. Saw someone saying they got the felhound one their first try and havent gotten the imp yet despite doing a lot of rifts since. Kinda makes me worried its bugged to be one or the other.
I picked up both today. I haven’t gone to the Barber so I don’t know what they look like. RNGesus be with you. 
How can I access time rifts?