The DG proc is better when you only dotting 1 boss. The EWH power relic gets exponentially better the more people you are fighting. To outright say that DG proc is the best I feel is false. Granted I'm lazy as hell so I run a proc and an EWH relic
I see where you are going with this. You are suggesting that because the proc is limited in how often it can go off, if you are dotting multiple bosses, you think the additional power is best. But the numbers show otherwise. The DG proc and DG power clicky are better DPS regardless of how many enemies you are fighting in PvE. The difference in DPS between the proc relic and the EWH power relic just isn't close enough that multi-dotting makes much of a difference.