Update 2: I've done some testing in reguards of dual vs 2h (some t6 rift and a GRift for every configuration). Here are my observations:
With dual wield the speed of seismics consume fury really fast, so i decided to increase CDR from 25% to roughly 35% ( i've lost some crit and all res) and now leap and seismic are near perfect sync, maybe some more CDR and GG. Still, between leaps, i had to use something to dump the fury generated by leaps and i opted to change Animosity with Rampage/Weapon Master and reduce the fury pool from 180 to 160, then i have changed Rend with Battle Rage(Bloodshed) to get back some of the damage lost on equip for CDR and a little dump of fury between leaps if needed (good heal from Life per fury spent too). Overall a more frenetic action and a very good damage.
Fastest Rift T6 out of 3 was 9 Minutes and GRift i failed lvl 28 for a bunch of seconds.
With 2H, Wrath of the Bone King (1400dps 25%cold), things go very different, due to the slow pace of seismics, i left CDR at 25% and increased my fury to 190 (i could reach 200 if i spend 10 more paragon on fury). Surprisingly i still need to dump fury, to not waste it, so i left my spec unchanged cause now Seismic Slam, Earthquake and Rend do a massive amount of damage. I've lost 10% cold damage but my overalll damage seems increased a little, even with a crappy rolled Wrath of the Bone King.
Fastest Rift T6 out of 3 8 minutes and GRift i failed lvl 30 for 20 seconds.
I'll do some more testing to see if i'll be lucky with density and reach a better performance, hopefully drop a better Azurewrath and Bone King. I hope in a Rhimehart to drop to test it, the change Blizz have done made me curious about the damage output of the proc. Let's prey RNGod.

Update 3: I've tested those Legendary Gems in these days, and selected some of them to use in this build. Let's go with the list:
Bane of the Trapped: increased damage on CCed enemies, and this gem will sinergize with herself at lvl 200 25, a must have.
Taeguk: increased damage after spending resource and increased armor, considering the high spam of fury spenders is easy to mantain the stacks, a must have.
Moratorium: 30% of the damage being staggered overtime with 10% chance to clear the staggered damage, it became my third choice in GRifts, so much hidden toughness.
Bane of the Powerful: Increased damage after killing an elite pack and +% damage on elites, an exceptional LGem but got replaced with Moratorium in GRifts due to my playstyle.
Wreath of Lightning: Mini conduit + movement speed, a good rune but propbably do not suit this build well, the movement speed buff is good for fast positioning only.
Enforcer: Increase pet damage and pets take less damage, the use of perma CotA doesn't mean this LGem is for it, in this build Ancients ar there to give 10% crit and act as shield, so i think this gem is wasted here.
Mirinae, Teardrop of the Starweaver: Smite on hit + periodical auto smite, this is a subpar with the mini Conduit one, the damage output is not bad but it's not the optimal LGem for this build imho.

Update 4: A fellow friend gave me a Rhimeheart on the ptr, sadly was already with a socket and gave it back but i tested the proc. Many says that the Frozen prerequisite is a limit, but as long as this build permafreezes anything, i saw it proc quite "frequently", not as much as a Thunderfury obv, but the damage is very high (i saw some 120/130 M damage if crit) and speeds up the trash disposal a lot. Rhimeheart looses most of the benefits against elites/champions and Rift/Grift guardian due to diminishing return on the freeze effect but still is a strong candidate for over 35 GRift. I hope Blizz will double the proc rate cause is frustrating that the rarest weapon in the game is subpar of others that drops more frequently.