Jennica's Ring only affects the Revenants non-pvp world drops, like Dragon Daggers and Glory Amulets. I don't know if RoW really affects their pvp-gear drops though. I'd say go with Ring of Life, if someone claw rushes you when you aren't prepared (saved me multiple times). For cannoning, it increases the chance that you will get PK'd so i wouldn't recommend it. I don't think theres any way around just killing a ton of them droprate-wise. Personally i've gotten all my drops from the Revenant Ork (Ruby Chalice, 39 Morrigan Javs and 1 Zuriel Hood) so i'd say the higher level the Rev, the better.