I use MHing to refer to bosses.
Lets think here, I've seen plenty of level 30s making 200K an hour at flesh crawlers which with an equivalent fishing level they wouldn't even come close to that amount. Furthermore, how on earth can you discount green dragons, specters, aviansies and their ilk? Thats probably the biggest part of monster hunting. As for those with high levels, they can do activities such as barrows, gwd, td's and high level slayer monsters that simply just blow skilling out of the water. The point is that in order to make more money than someone your level doing spectres, drags etc they would have to have like 99 hunter and be no-lifing grenwalls or some such. Even then, tds would put them to shame
Now, as for the "afk value of fishing" or whatever that you seem to put in such high regard, Its obvious that giant skeletons or bandits might be more your speed.
I was just using fishing as an example of how profit per hour is actually higher then it seems, because I suspect the majority of people who fish, train woodcutting, or other skills of the same type, train them in this manner. They spend little time actually performing the skill, and they still are able to perform at a decent efficiency while spending far less time actually "skilling". This is exactly the case with farming.
I have done the majority of my melee training through slayer, with the occasional chunk of xp gotten while camping for drops such as black masks, whips, tokkul, or charms.
Also, as troacctid stated, high gp/hour rates can be obtained in farming ranarrs, or making unf pots. Neither of these takes very long to achieve, ranarrs are 32 farming, and you can make unf pots almost immediately after finishing druidic ritual. This is slower xp with much higher monetary yield. The same goes for boss hunting, the xp/hour isn't really that great at bandos, armadyl, TDs, or corp. But the profit is much higher.