Thats not how it works. The results Simc give you are independent of rng. Sure felblade involves rng, as does the whole class with beign reliant on crits, demon blades being a thing, anger is also a source of quite a bit of rng. On average felblade is 5-6% dps gain over bloodlet if executed properly. You don't need proc luck at all for it to be better.
And 5% is not a small deal, it is not so easily drowned by a bit of rng. If it was like a 1% difference you could argue consistency but int his case, clearly not, especially not since felblade has a decent minimum value since it has fixed CD on top of being able to proc, its never all or nothing with it.
First Blood also does nothing for AoE, it only affects the first target hit by BD. You can get extra priority damage due to balanced blades in AoE situations, but your true AoE damage is entirely unaffected. So the assumption it was for AoE is entirely wrong from the get go.
I agree that it is kind fo weird though and pretty unintuitive given the usual design. Since you have essentially 2 different ST options and one cleave option, tuning aside it is weird to have that and they are also fixing it in 7.1.5 so you have one ST, one cleave and one AoE option which makes the tier more well-rounded design wise. Tuning will be a different story again and only time will tell it.
Before derailing further though. My point is that felblade is currently worth taking on ST heavy encounters like Odyn, Guarm, Nythendra and maybe even on stuff like Elerethe if adds die so fast that bloodlet doesn't do much damage on the adds. Hell, even Cenarius mythic with the nuke tactic and Xavius might be decent options, since the actual cleave is a rather small part of the fights and might also be of no huge improtance, so focussing on priority damage + a bit of extra gap closing might prove more useful.
The anti-synergy with anger can also be viewed as helpful, as it makes felblade closing the gap between ring owners and non-owners since the difference shrinks from 10% to 5% and thats especially why I can't promote felblade enough right now. While things are changing drastically in 7.1.5 we actually have an option to play around not having our strongest legendary until then and given the huge waves of complaints we see here currently involving the ring this really shoud help this community realize that they are less dependent on having the ring than they think they are.