The new easiest way to permablock will be to run a hybrid tank with shield and frost staff, and maxed reduce block cost.

With a moderate stamina and magicka pool, you'll be able to block for quite a long time still, and when you get low you swap to the other pool, allowing recovery to kick in.

I plan on doing this for my warden tank. Will use a regen food like red frothgar or jewels of misrule, and the bull netch for stamina recovery. On shield bar, blocking time will be extended by the netch stam return and constitution/black rose. While blocking with the shield, magicka will be recovering. Once stamina gets low, make sure the netch is refreshed then swap to frost staff; blocking now uses up magicka while my stamina recovery, constitution, and the netch quickly restore my stamina pool.

The only fights where prolonged blocking is necessary typically require you to do nothing but block, taunt every 15 seconds, and use ultimates, so you're not spending resources on anything else. In any other situations, permablocking isn't usually necessary.