Why do people hate Healing Breeze?

Basic reason is because you are more able to sync with your similary specced coleague.

two simultanous prots lading on spiked target followed by one heal do same as two prots from prot monk and two heals from heal monk: as result your total pool of energy at monks is 5e ahead if you have hybrids.

its about rational use of energy. if your specialized monk is full and party needs straight heals, all he can do is waste energy on DF healing while healing monk burns trought it and gets headaches. similary, if you need protection and straight heals are mostly irrelevant, same happens in reverse. if you have hybrids, they both use moderate amound of energy and are both ready for next encounter faster because they regen in meantime.

its about worst case scenario where one monk is on ground and your remaining one can still take care of most stuff. This is perhaps the most cogent argument I've heard for why having two hybrid monks is a good idea. (Usually the "argument" in favor of hybrids sounds more like: "Hyrrid is the meta LOL stoopid NOOB go uninstall QQQQQ!!") However, it's also an equally strong argument against running a single hybrid. What do you do when your counterpart isn't another hybrid, but rather Mhenlo, or Redemptor Karl (ung!), or a PUG monk who can't/won't go hybrid with you? I think you'd want to avoid the situation where you have 1 & 1/2 bars dedicated to either heal or prot and only 1/2 a bar dedicated to the other. You're going to end up burning through your energy pulling double duty on whatever your counterpart didn't spec, and probably doing a poor job at it due to a short supply of recharged skills (which is, in turn, due to not having enough skill slots dedicated to the task).

I might add that this puts the H+H player in a real quandary: Is it worth it to spend two of your three hero slots on hybrids to make this sort of backline work? My opinion on this issue is that the performance gap between damage-dealing heroes and damage-dealing hench is much bigger than the gap between monk (or monk-replacement) heroes and monk hench. So, I try to make do with two hench as often as I can. And, when I can't, I try to make do with 1 hench and a 1 hero specced to specialize in whatever the hench is not.

I might add that this puts the H+H player in a real quandary: Is it worth it to spend two of your three hero slots on hybrids to make this sort of backline work? Definitely not worth two slots, but definitely worth one slot IMO, just to get an LoD monk in your party.

I bring Ogden (LoD hybrid) on all my characters, and then Lina as the 2nd monk on my non-monk characters.
This way at least you can have one LoD monk in your party, and at the same time fill in the prot holes left by Lina's bar, namely Aegis, a hex remover, and a second condition remover.
I find Lina to be decent, except that she sometimes casts ZB too much and PS not enough. She's actually pretty good with SoA, SH, and Dismiss, but a little hit and miss with RoF. I'd rather deal with her though and leave my last 2 hero slots for damage dealers.

And no, Ogden does not pack Healing Breeze.

This is perhaps the most cogent argument I've heard for why having two hybrid monks is a good idea. (Usually the "argument" in favor of hybrids sounds more like: "Hyrrid is the meta LOL stoopid NOOB go uninstall QQQQQ!!") However, it's also an equally strong argument against running a single hybrid. What do you do when your counterpart isn't another hybrid, but rather Mhenlo, or Redemptor Karl (ung!), or a PUG monk who can't/won't go hybrid with you? I think you'd want to avoid the situation where you have 1 & 1/2 bars dedicated to either heal or prot and only 1/2 a bar dedicated to the other. You're going to end up burning through your energy pulling double duty on whatever your counterpart didn't spec, and probably doing a poor job at it due to a short supply of recharged skills (which is, in turn, due to not having enough skill slots dedicated to the task).

I might add that this puts the H+H player in a real quandary: Is it worth it to spend two of your three hero slots on hybrids to make this sort of backline work? My opinion on this issue is that the performance gap between damage-dealing heroes and damage-dealing hench is much bigger than the gap between monk (or monk-replacement) heroes and monk hench. So, I try to make do with two hench as often as I can. And, when I can't, I try to make do with 1 hench and a 1 hero specced to specialize in whatever the hench is not. Yes, it is still worth it.

for pugs, that pug would still be better off than standart duo healer situation. also, you are unlikely having to do twice as much in attribute that your coleague didnt spec due to nature of fact that you can fulfill role of either side of monking without much strain.

you still gain doubling your monkage in attribute you both specced, but when it comes to attribute only you specced, you are in no reall disadvatange over pure heal/pure prot approach.

for heroes, it is harder, unless you H/F /use heroes with one friend/. I would not use hero monk at all if possible, tbh, but rather pack some heroes with "duality-concept-aware" build. as you said, when henching, you miss damage more than defence, but heroes can bring both to table, so its silly to use pure defensive hero like monk. with some wards and some weakness on enemies, your hench monk can handle a LOT.

only case you want to run hero monk is vanquishing 4/6 man areas, where you do want hybrid because of limited party slots.