I really don't see why people who PvP are QQ'ing about the "no stam regen while blocking". However, I do see why PvErs are QQ'ing about it.
In PvE, in end-game "content", such as trials, DSA, and pledges, it is impossible for a tank to release block without getting one-shot by a boss. For example, a tank cannot release block while fighting the Mantikora in Sanctum Ophidia, without totally getting one-shot by him.
So, as a solution to this, I believe that this "no stam regen while blocking" should apply only to PvP, and not PvE.