Thanks for the Video
When you say
Why exactly do you use a regular tank? Considering a warlock with sufficient gear and specc will have something like 70% damagereduction against shadow (before resistances!) and about 45k health (PvP equipment and highstamina rings/trinkets).Shadow Lance will hit for 20k and Empowered Shadow Lance for roughly 100k unmitigated, which is why it's recommended to put a regular tank class on Keleseth instead of a ranged tank.
so if he takes a full 100k hit without any nuclei (unlikely but lets consider the worst case) he will still be alive with about 15k health.
As i see it a special warlocktank would be much easier to heal and will have less trouble collecting the nuclei, on top of that the uptime of nether protection will even be higher than in normalmode because of shadow prison.