Personally I think they should do this with PFF:
- regenerates faster the lower your current shield amount is. For example, at 30% it regenerates ~20% per second, at 90% it regenerates ~5% per second.
- the amount the shield absorbs is lower as the shield amount is lower, For example, at below 30% it absorbs 50% damage. At 100% it absorbs 100% damage.
- blocking no longer affects regeneration speed.
- shield amount scales with all super stats.
- Regeneration speed no longer scales with super stats.
- shield amount is no longer affected by any +healing modifiers.
So now it's viable for cosmic tanking as it will give good mitigation under repeated heavy blows, and will give really good mitigation for that first attack you take. When going up against swarms of enemies you will similarly start the fight with really good mitigation, but under continued pressure that mitigation will fall - Field Surge can be used to extend this initial period of really good mitigation. In both cases healing becomes relevant again because under pressure eventually you will need healing to survive.
This is also nice and thematic; at high power the shield is an impenetrable barrier, while at lower power it becomes more of a dampener, exactly how you would expect something like that to function. The problem of "my passive disappeared" has disappeared.