If your hero already has a lot of hero skill on resource yielding bonus then you wont see a lot of difference because they already might have a lot of bonus ... so try it without the hero ...

First he said 50% not 75% ... anyways like I said I've done it and when your hero gets about 265% yield bonus from knowledge, hero skill and equipment an extra 50% is not that much ... When I tested it it took 88% of the time with hero than it usually takes when I used a 50% resource yield speed up where as with my troops without hero  which had 66% bonus from knowledge it then took 76% of the time when I used a 50% resource yield speed up.  From what OP posted it looks pretty similar showing 90% (and when I did mine I calculated to the seconds).  You have to consider that there is already some yield speedups going on besides the specific boost you start at 50% or whatever % ...

Those yielding boost are great when you are sending out 10 non-hero farming marches.  Usually a minute or so before the global events end, I send out my 11 marches to all the unoccupied liars and grab all the big full ones of resources that I need, usually iron.

The max # of march may be 18, at lv 31 and all march knowledge completed.

I like to use these resource yield bonus when I am going to send out a lot of marches and send them out frequently (so they are small marches and I won't lose a lot of troops if they are attacked, inevitably when someone comes in to attack I will lose the march closest to where they transported to but usually I can "pull" the others before they can get to them). 

When sending out smallish marches, I try to send out a batch just before the 1 hr ends, but the marches must be at the rss site before the timer expires.  I misjudged today and 1 march didn't make it in time and for 30k troops, 475k rss and a 75% reduction it took about extra 28 minutes to complete.

Yes I do that a lot also and yes sometimes you don't time them all perfect.

i see that with this new knowledge and shaman we have many more ways to test yielding and i had done it with heros double on so i had 2 heros with centurions gear and shaman with 2 equipments and 75% boost on with lvl6 in spoils of war new 2 of them in economics and 10 on previous spoil of war which gets huge difference but a hell lot of rss.