I wouldn't say Dynamis Lord is a lost cause and a waste of time, by any means at all. Shadow Mantle and Shadow Ring, while being mostly status items, have their uses. I can't think of many nend-game items that are NOT situational (which Shadow Ring and Shadow Mantle, are too). Almost all AF2 are situational for most jobs, so saying Shadow Ring and Shadow Mantle are useless, is like saying AF2 is useless. But still, there's people out there who only do Dynamis ot get AF2.
Personally, I do Dynamis for fun. I don't do it for AF2. I do it for the fun, and for the story. I want to at one point kill Dynamis Lord, just for the sake of being able to say I've done it. I believe lolDynamis think the same way.
AF2 is situational, Shadow Ring and Mantle are situational. Almost all end-game items are situational. You can't deny that. You can do most any end-game event without these items, they won't magically get you the win just because you have them. They are situational, and makes the owner just a little bit more pimp. And that's the reason people want them.
While they are not important themselves, and won't magically get you the win, they do make it easier. Every time Shadow Mantle kicks in, is less damage taken by the person who owns it. This adds up, and makes the WHMes spend less MP. That's how all items work, they don't suddenly make the owner a god.
The reason people say Shadow Mantle and Shadow Ring is useless, is because they, themselves, know they can't get it. What they can't possibly get, is not worth getting for them, and is deemed useless. I can assure you, that those who have a chance at getting it, will think the complete opposite. And I can assure you, that if you had the chance of getting it, you wouldn't say "No".
So by saying Dynamis Lord is useless, is nothing more then saying you don't think its worth it. But obviously, lolDynamis thought it was the opposite. They wanted to kill Dynamis Lord for several reasons.
And I feel its worth repeating. Almost everything, including most end-game items, are situational. And almost all of them can be replaced by something else, that can almost completely copy the effect of the item. So seriously, why are you saying they're (Shadow Mantle + Shadow Ring) are useless?