Calling regen mitigation is a stretch, as it doesn't actually secure your own health pool and is itself a sub-type of healing (which in its broader form typically gives us our 4 categories of sustain:
- "%DR" -- scaled and max-eHP-increasing but duration-limited,
- "Shields"/"Barriers" -- flat and max-eHP-increasing but (somewhat) duration-limited,
- "%Recovery -- scaled but not max-eHP-increasing and window-limited (as per Death Knights in WoW),
- "Healing" -- flat and not max-eHP-increasing but without duration limits).
Because the duration of shields tends to be so high (apart from perhaps TBN) relative to the amount of time required to break them, meaning that shielding can rarely ever go to waste, heals tend to just feel worse. Give
every barrier only 7s to be popped or cause them to decay over time, though, and things might not feel quite so skewed against pure healing. Just some food for thought.
:: Further, if by Regen you did mean a HoT, then aye, that is purely a limitation. At least,
in itself, just as DoTs are weaker than direct damage... unless buffed accordingly (thereby allowing for one to effectively double/triple up on the density of their high-ppgcd soft-CDs by fighting multiple enemies at a time to a higher total damage than others can manage). (Similarly, %Recovery is generally the 'worst' of the above main categories unless overpowered in terms of maximum output. Again, see WoW's Blood Death Knights.)