It depends on the content. Some attacks must be blocked and can not be dodge-rolled, like the Shehai stage when fighting the Warrior in Hel Ra.

I haven't used block in PVP since Gaze of Sithis released, outside of blocking stuns.

For PVE, that block mitigation is great in solo encounters. Especially in preparation of big hits in the Archive in later arcs.

depends on the build

As far as I understand, Block Mitgation doesn't work for shields, so if you're using Hardened Ward and Blocking, you're only going to reduce the damage you take from the part of damage that goes beyond your shield. Additionally, it's my understanding that if you're bracing/blocking, although you may receive no mitigation due to the shield, you still lose stamina and of course, cut off your stamina recovery.

Eg. if you took 10k damage and you mitigate 50% via block, you may expect 5k damage taken, but if you had an 8k shield, the 2k remaining damage is the only part that migiates, so you take 8k + 1k for a total of 9k.

I think it's entirely situational, like maybe your magicka pool is getting low, but you have plenty of stamina, you could opt to use Aegis + Blocking and occasional Hardened Ward vs spamming Hardened Ward back to back.

Also it's not to say it's entirely not worth it, in IA with Mauraders dealing like 60k light attack damage. My Sorc has 42k hp and can basically double that with Ice Staff Heavy + Hardened Ward, yet I still need to block because even the additional 18k remaining damage would put me at half health with all the other damage coming in. Blocking is necessary at that point to survive because the damage taken is well beyond what I can shield once every second. If my shields were enough once every second, then blocking would be useless, only burning my stamina pool and reducing my movement speed.

For PVP, I'm thinking in an outnumbered situation where you drop below 50%, and maybe there is a Templar beaming you, you may want to pre-buff with Aegis, then spam Hardened Ward during that 5 second window to get back to full because the damage taken can easily exceed what your shields can block.

All this to say, I basically never block outside of avoiding a stun from something like Meteor, and because of my playstyle, I also found Gaze of Sithis to be very useful on Stam Sorc for a few years before undodgeable crazy high damage like Templar's beam basically became a death sentence.

But correct me if I'm wrong if my feeling on this is incorrect. Maybe the math works differently.