Shields already regenerate pretty quick. I'd even go so far as to say they compete with Master Chief's shield regeneration time. What would be more useful is a decrease in the time it takes to *begin* regenerating the shield, both before and after it is broken. Let's call that "repair time decrease."

I have a couple UV ideas, though:
*sword/gun ASI
*increased normal/pierce/elemental/shadow damage (rare)
*bomb fuse time decrease
*charge speed increase (walking with weapon charged, applies only to weapons that make you walk slower)