Fel Eruption is only a DPS increase in 2 situations.
All encounters except one, Opulence.
It does less damage than demon’s bite, and it uses fury instead of generating it. Using it in a standard rotation, when in melee range, is 100% a dps loss over not even picking a talent.
“It does less damage than demon’s bite” duh. You’re casting Demon’s Bite on average 80 times per encounter in a raid scenario. Also, you don’t pair it (Fel Eruption) as a standalone, you pair it to dump fury OR with eye-beam (assuming you’re traited for the max fury regen).
About those logs you linked. Don’t just look at talent selection and numbers, look at ability usage. They are not using fel eruption on CD, or in place of demon’s bite. They are using it for the stun, not the damage.
No one said that you’re using Fel Eruption on CD or in place of Demon’s Bite. Why would you even think to replace Demon’s bite in general, lol? You’re just adding substance to support a distorted argument. Additionally, you are using it for the damage. You’re using it for the damage and the stun to either control adds, or if you’re on add control to keep a little bit of damage on the boss. It gives you an extension of range to DPS out of an area unreachable by other melee.