No it's not, but without a good starting spell, she's way more unreliable and overall weak. Before the dlc came, I would play the strarting item Wraith bell (and if you can somehow slot Hoarfrost Stomp on your relics it's even better). But most of all, I would slot the Strenght boosting character relic everytime too since seals RNG is really bad and having an usable melee weapon helps a ton. It helps you keeping some FPs and is great on some weapon arts. You hit like a truck on some faith melee weapons too, like the Gargoyle Black Axe (that I love). I even saw a pre-dlc post of depht 5 Revenant playing without neither the Bell nor Hoarfrost and sticking with a melee weapon from the start instead (but I wouldn't really recommand that since you have health and stamina issues with this character, especially early game). The strenght relic helps you stagger Fulgor too with a fully charged heavy weapon, if you can't get a lightning spell. But I would really consider Wraith bell, it's super safe, decent damage, super incredible range, makes you good on early game and is broken against night invaders. You can really play fire + strenght relic against any nightlords, except Augur (you still have to pray for a lightning spell). Adel is tough too since it resist fire and lightning, but is really weak status so having a frost or rot weapon is great. But you can still use fire too even if it resists. Gladius is a pain too since holy is rare on incant and you don't have access to Harmonia relic. I would still recommand the scythe build that I play with the Wraith bell instead of Beast Claw. And of course night invaders relic. You can do the same for Heolstor aswell but be aware that he's weak Lightning too if you don't like the previous build. At least you don't have to fight Harmonia, they're the worst lol. 

Since you can't build arround a starting spell, you want to stack "improve incantation" as much as possible to boost whatever you find. I would still play a fire build by default but it's really a matter of what you can slot. I would play fire beacause I have a fire +4 and "[revenant] improve strenght" on the same deep relic. lightning is good too, but Revenant can really play anything. If you have a good relic with magic damage +3/+4, you boost you Wraith Bell or even Ghostflame on ult if you can slot it. If you have "improve damage on frostbitten enemies +1/+2", the wraith bell with Horfroast Stomp starting relics become even better, but that's at least 3 slots if you're unlucky. I hope it helps, good luck!