I saw a video today where a guy was testing eitr regen with robe vs armor and it looks like the 100% regen buff is BS. Or at least it was vastly decreased due to rest helping with regen as well. With his test he regenerated 35 eitr in 5sec with the robe vs 7sec with the armor.

I want to test it myself with a bigger eitr pool to see if the difference makes it really worth it. I always trusted the buff without really questioning it. OTOH I dont use magic a lot, I just like slicing things with my sword.