Shield spec is still a strong spec, it's just not as grossly op as book spec and since book is retardedly easy to play it currently makes no sense to go for a spec that needs more effort to play and still get worse results.
But instead of toning down book, they buff shield, so it gets closer to the former. "**** every other healer in the game, as long as my class shines."
Currently many premades run double WP / DOK in dps and book comp because of how insanely strong they are. If the classes don't get toned down we gonna see them run triple WP / DOK: Shield, Dps and book / chalice.
Maybe then the run of the mill player questions if the class is a tad bit overpowered.