Oh you can be sure when I pick hammer it is nothing less then what Thor hammer brings destruction
this depends - some Delve trinkets are played in mythic raid (like 2 candle trinkets), and some others are pretty good but yeah a bunch of them are bad indeed.
If you wanna see for yourself - check e.g. mage mythic logs in nerubar you will see like 5-10% mages play Candle confidant from delves on mythic bosses and some of them are in top 10 parses.
Well as a hunter main everything is F:D
Even some personals sims with dungeons/dummies they are very poor .
The 0.8% ~1.2% proc dmg is 2 low considering that the void reaper’s contract can proc up to 4.5% in some fights .( i won’t talk about the mad queens since biggest crit was 19 mill 
with trueshot )_
The delve trinkets for delve content are pretty poor optimized (at least for my dk~hunter and warr)
If they are accessible to the playerbase at least make them to be competitive in order class-specs to have more options rather than forcing everyone to play the same .