Perhaps make damage mitigation something with some actual play to it. I think skills like Sheltron and The Blackest Night are a step towards this, but it could go a lot further.

Say for example we get rid of autoattacks on enemies - instead make them attack in ways that you can see them winding up (either through animations like the Diresaur models or with AoE warnings). Make block/parry something you can do at will rather than an RNG chance. Maybe for single-target fights like bosses you have to block in the correct direction also (attack coming from the left, from the right etc.).
Perhaps even if you block/parry enough boss attacks in a row, you can get a little quicktime event where if you succeed you throw the boss off-balance and it takes increased damage from all sources for a short duration.

I don't know if the game's netcode could handle a system like this, but with some judicious client-siding it may be possible.