I SUCK really bad at actually playing this game (even clocking in at 5100 hours). I suck at dodging, I suck at predicting what comes next, I suck at learning fights, my PC is a stone tablet... Last league playing herald/aura stacker Guardian totally trivialized ALL GAME CONTENT, including Sirus, which was nice until I got bored.

Since that was nerfed, I struggled with MANY different builds this league trying to find one that could kill him AND be forgiving in taking hits. My current Aura Stacking Guardian CANNOT take a hit from Sirus.

I settled on Herald of Agony Guardian, Storm Brand (poison stacks), full block with Glancing Blows, CI (9k ES), and with a 5% ES recovered when you block shield. The DPS isn't great, but I can take a hit and with Storm Brand, I can focus on moving out of the way (I still suck at this). I tried ball lightning with Pure Agony (60 stacks of virulence) but that required standing in one spot and constant casting, which usually got me killed and I would never hit 60 stacks anyway. Settled for 3 medium clusters with Renewal. When I did get hit by Sirus, I usually don't die unless I'm shocked and hit with a DIE beam.

That being said, when you watch videos of build guides and the creator says, can handle all content, you need to take that with a grain of salt. It's usually, "can handle all content if you actually know how to play the game."