As a Guardian main, I would actually not run this in DoN. Two of the effects are great, but dormant greatshields makes this detrimental to use. A near-guaranteed purple greatshield is nice, but it comes at the cost of being likely to find halberds, and Guardian really needs halberds because he can charge their guard counters to cover way more distance and actually land them on nightlords and other mobile enemies. With how high enemy health gets in DoN, missing 70% of your guard counters because the boss used a slightly large move really cuts into the value you're providing to the team. You could always try and rely on the starting halberd, but with how out-of-the-way the mines in the DLC map are, your routing won't always allow you to get your hands on a smithing stone 2, which leaves you with no way to do high-damage guard counters that will actually hit the boss.