I'm cheating a bit here as this is not really a tierlist, but still this describes the various legendaries and when to use them. Generally speaking, all of these are within 2-3% on single-target, so it works out to be mostly about what alternative pieces you have (if you have really good gloves but weak rings, it might flip the priority for example)
Previous all-star, now after nerfs relegated to being a roleplayer - it is still solidly the best legendary on 2-3 target long living cleave and is still alright on Single-Target but is by no means required. It interacts quite poorly in practice with boots and I'd advice against using both normally.
The new all-star, provided you are using Bloodtalons, there are very few situations where this legendary would be directly bad. It is however not as strong as people sometimes believe. I'd certainly recommend using it both as it makes the rotation slightly easier and it's always at worst an alright choice.
Got a minor buff, but is still mostly a situational choice. Really powerful on encounters where you have forced downtime from the boss for example as it allows you to store (pool) more energy while away from the boss. Additionally it simplifies cases when you could use a lot of Predator procs and can turn out to a solid dps increase in those cases.
Very solid trinket, like most stat sticks. Unless you have really good trinkets, it shouldn't be underestimated - the effect itself is mediocre unless you are on a big aoe fight, but just being a stat stick at a high ilevel makes it a compelling choice in many situations.
Probably the strongest patchwerk legendary effect, it's effect generating between 2-3% on a normal fight. Sometimes better (like on Odyn) and sometimes mediocre. The belt itself doesn't have a lot of stats which holds it back. Never really a bad choice, usually not going to be amazing either. Easy to use as it doesn't change anything for you and always performs decently. Good choice in a lot of cases.
The strongest legendary by a reasonable margin on fights where you use thrash a lot. Scales really well with targets, works well with both BrS and BT. You probably want to use it on most fights in Nighthold if you care about minmaxing your damage output. With T19 it gives you a small dps increase, not really worth using for pure single-target but it's a nice bonus on a fight with some AoE.
Solid (probably second best for patchwerk) single-target and good for 2-3 target cleave, being legs means it bring a lot of stats which increases it's relative value a lot compared to the other legendaries. Never really a bad choice, but can occasionally be a bit awkward to use.
We have a lot of ways to proc it, but the problem with Sephuz is that haste is simply not that valuable to us, especially not in this proc form. The only legendary I'd actively recommend against.
A big statstick, with a utility effect - Worth including in your Sims as the massive stats makes it competetive in a lot of cases - the effect itself carries no real dps increase normally so you have to evaluate the utility value of the effect.
Same as Eko-Wraith, very solid statstick - can occasionally be worth it over a dps legendary, and never a horrible choice, but if you want to use it over something else will usually depend on how you evaluate the survival utility effect.
Decent choice if you don't have 2 other legendaries, but otherwise not amazing. Additionally being in the boot slot is not a great spot to be as it then ends up competing with Ailuros Pouncers, alright for alts but I'd probably not bother getting it over something else