If all they were bringing was reconstruct you might have a point... but that would be like saying bards only have cure spells. The class will bring alot more than just reconstructing to the table. Bladebarrier for one, as you noted, and they will be another source of undispellable buffs, that stack with bard buffs. They also use grenades, including healing grenades... which may or may not be useful. They have access to both positive healing and reconstructing. They seem to be self sufficient. If they end up being the ultimate umders then they can also bring ALL the arcane and divine buffs as well as the new artificers.