This is specifically centered around Havoc DH but I’m sure this is just as applicable to Vengeance. TL;DR at the bottom.
As the title suggests, yes, implementing Legion legendaries into talent choices was a logical move. But the choices made with Havoc give the impression that very little thought was actually put in. Endless Hunger from Anger of the Half-Giants and Cycle of Hatred from Delusions of Grandeur are now essentially lackluster talents that fall behind the other options on their respective rows.
Now perhaps they could be made more attractive options with some math tuning, but that doesn’t hit the root of the problem.
Yes, AotHG and DoG were some of our best legendaries and were used often, but they weren’t the best because they added any extra complexity or changed up your rotation. They only offered basic throughput.
AotHG was mandatory throughout all of Legion simply because it passively upped your resource generation. That’s not compelling or interesting. And passive CDR to your biggest damage cooldown was only fun when it didn’t come at the cost of your rotational complexity.
Conversely, Raddon’s Cascading Eyes and Loramus Thalipedes’ Sacrifice are examples of legendaries that actually affected your decision making process. Lining up enemies to ensure maximum damage/CDR is a thousand times more interesting than passive throughput. Chaos Theory: even a passive chance at a damage proc is more interesting than passive throughput.
Achor, the Eternal Hunger’s effects could have very easily been baked into a defensive talent option. The damage bonus offered by Mo’arg Bionic Stabilizers could have been made into some sort of talent option that added complexity to Throw Glaive - an ability that now feels robbed of all depth with the removal of Bloodlet.
Do you know what else was a compelling ability we had in Legion that we no longer do? Fury of the Illidari. Even without the artifact trait that made it explode, it was an insanely fun ability. We were a brand new class. Of all classes, Demon Hunter should have seen its artifact abilities baked into it’s core as either talents or generic cooldowns.
All in all, there are far better candidates for talents than the ones you chose. Please consider replacing Eternal Hunger and Cycle of Hatred and stop the process of pruning depth and complexity from a spec that already suffers the criticism of an extremely simple rotation.
TL;DR: You could have picked ANY other Legion legendary to turn into talent options, but you went with the absolute most boring ones.