I was sad to see a few points towards Hero's Key disappear from the epic monthly quest reward.

The rewards are nice to get if they come without distorting play but are surely not worth targeting as a primary objective.  Hero's energy is certainly better used in CvC etc.

I have always tended to agree on your 

'The rewards are nice to get if they come without distorting play'  element,

so mostly would not go out of my way to get something I didn't do already, but if I was near the trigger point , or it was beneficial in some other part of the game and it would make it worth my while then I would do it, especially for the rare occasions where I might get to level 4 , or the even rarer level 5.

The daily quest has recently updated, and I shall be fortunate if I get two rewards, the rest (for me) are impossible or would involve extra  spending.

Growing too fast just puts things out of range, so I gave up fairly soon on my big account,around the time I almost got gold on the monthly quest, but a maintenance shutdown robbed me of the chance to complete it.

This is not the first time they changed rewards on the quests,or elswhere, often replacing them with unusable (to me) items.

Marks of resolve are no good if you can't get into Helheim any longer, not that going there was that big of a deal, removing the option,like adding restrictions to achievements  is, and  I am left wondering if I still get the  few bonuses I already earned, or they also cancelled what they stated where 'permanent bonuses'