I might be wrong on this but it seems the bar also fills up over time regardless of players hit by attacks.
Irregardless of that, the DPS check is still insanely high and the comparison to Dhuum‘s first clear is pointless since that encounter was about understanding its mechanics and not pumping out a ton of DPS while avoiding not only death, but even being tagged by attacks.
Like I said before: it may have been intended this way but I doubt it. Having a look at it to confirm that certainly can’t do any harm.