Tbh I wouldn’t call myself the 2h melee lightning expert for endgame, Warder, Druid, Vindicator, Elementalist and Conjurer can all work. Most of these also for 2h ranged Primal Strike on top.
This is what I found, it seems like Warder is an all time forum favorite for melee:
Conjurer: [1.1.5.2] Korvaak's (ab)user. Ultos 2H Lightning Conjurer
[1.0.6.1] Primal Ultos - A supercharged PS >Conjurer< of Storms 150-170 Gladiator in 8:50
Druid: [1.009 - 1.1.6.2] Lightning God Rises - 5:45m Crucible, SR 75-76, 7s Mad Queen, no greens melee Druid [g3][c+][sr]
Elementalist: [1.1.4.2] The Lightning Hammer- Ultos 2h melee Elementalist, Gladiator in 6:45 on average
Vindicator: [1.1.3.1] Lightning 2h Ranged Vindicator, Gladiator in ~ 7 minutes
[Ranged Lightning] Crit Striker - Thunderous Strike Rifle Vindicator
Warder: [1.1.7.2] Thunderbolt - The Primal Strike Warder without Savagery [c+] [sr+]
[1.1.7.1] Thunder and Lightning - The Primal Strike Warder [c+] [sr+]
[1.1.6.2] Thor - 2H melee Primal Strike Warder without Savagery, SR 65+
[1.1.4.1 - 1.1.5.2] (2H melee) High Voltage - Primal Strike Warder [c+] [sr]