Warding Energy Lore - will increase total shield energy points and improve the amount of damage that the shield will absorb. Note that Warding Energy Mastery (75 spent points) does not enable shield regeneration while in combat; the regeneration speed bonus is applied to out-of-combat shield regeneration only.
Much general information for energy shield usage is given in the article Energy Shields.
The Block mod increases the Damage Mitigation mod by an absolute amount, not a %, it also does not give % damage mitigation.
Pros and Cons
As a buff, a player doesn't have to worry about if their shield is up and running. (Unless it's energy is all gone).