Personally I like the clicky power relic over the EHW static one, but that's mostly because I've gotten used to clicking it on CD or sometimes saving it for big damage phases (e.g. Kephess TfB)
Some of the others in my raid group hate the clicky relic as they keep forgetting to use it on CD. For them, the EWH power relic is better.
The proc damage relic is definitely worthwhile. I use the Kinetic Tempest one, but that's due to the armor penetration on my Commando.
Ya as a slinger I hate trying to use the activate relic during boss fights like in TfB where I have to get up and move over and over (thus losing a lotta the activate phase bonuses)