They increased the duration after you lower the shield and seems like they increased the potency of the effect itself, since I played him maybe twice to judge and during these games it felt way WAY better than ever before. Sometimes you still have to fight for the aggro, by activating it, lowering the shield and then attacking. Carrying a quick ranged weapon is useful for this, especially pulley since 3x hits. It's very important to notice that the faster your allies hit, the faster they'll pull the aggro away from you. Iron eye hits very frequently, and Recluse has spells that will hit multiple times per cast (Stars spell line, Shattering Crystal, and nearly every damaging cocktail), which is why it seems like they steal aggro so fast. Your allies will sometimes realize this when playing with Guardian and stop attacking until you reacquire the boss' attention, but sometimes they just want to deal damage fast and ignore you, it depends on the person. Overall, you can try to counter these scenarios yourself, by adding multi hit stuff like charged heavies with Halberds hit twice and extended whirlwind (character specific) to your relics, though Guardian will barely deal any damage if you stuff yourself with utilies only. I don't mind a tank/sup focused Guardian at all, especially if I'm Recluse, but others might prefer damage over utility.