Transitioning Over to HM -- Any Help?

No.

First of all, neither of those is a great build for general PvE. Sabway is designed for 4-man areas, so it has a lot of compression and compromises that aren't necessary for 8-man teams (even if 4 are hench). Discordway is downright mediocre.

Second, and more importantly, your problem is that you don't understand the game mechanics and monster design well enough to succeed. Ultimately, you will have to learn that. Sabway/discordway won't help you learn. They will only give you a small, unearned boost of effectiveness. As soon as you hit a patch those builds can't handle, you'll be right back to square one. You simply can not go around screaming how easy this game is and how people that shouldn't be able to win win it and then make this drama.
Disco and Sabway will handle pretty much all the content in this game. It might not be the most efective way of doing it but it will work.
And if nothing else - it gives the players a chance to actually win instead of failing continuously which in turn removes a lot of frustration and it gives the player the chance to experience content and learn.

Those two teambuilds are completely sufficient ways to experience HM.

Lastly is experience... my first few tries at HM had me shaking my head & saying NFW... now I can't see doing NM. THE essential part.

Ive found that a good way to get this experience is to tag along with people who know what they are doing, for missions, and to "solo"-vanquish easy areas (~50 npcs at first, then build up) with a 3-necro-team.

It's a pity that only certain builds work in HM, it seems, but I suppose that's just how the metagame goes. Some builds work better in HM than other builds, however this does not mean you need to run them.

In HM you need to be able to do some serious damage. Foes have more health and higher armor. When you fail first make sure you were killing foes fast, only after that look at defense.
Don't start out in 4 player areas, those are relatively hard compared to 8 player areas.

Make sure you have the best equipment you can afford, specially runes.
Have as much armor/health runes as possible, try to avoid superior runes unless you need to use for a breakpoint. And compensate as much as possible with vigor runes.

Now some comments on damage mitigation.

First of all, make sure the team understand that the monks are there to keep players doing damage, not to keep them alive. Keeping players alive is only a part of keeping them doing damage.
When looking at builds look at what disables your team from doing damage. Counter this. I'd say the main problems are conditions like blind, cripple, daze and such. Most conditions are annoying, but you can outheal them. Next some hexes here and there, but most are not that bad. Sort condition removal and hex removal out first.
Only after your monks decide on this they can look at straight healing and protection.
Make the team understand that only one or two players should take damage if possible. Those players should have some skills/equipment that prevents some damage (+armor mods/runes/skills, shields and such). The rest should keep back so the healers can focus. When aggro is broken it's time for the monks to use skills like Protective Spirit and Aegis to protect the casters of the team. Using PS on someone who's dedicated to holding aggro is probably stupid (mitigate by other means), unless there is a huge risk of armor ignoring spiking.

Mitigation also includes aggro control, learn mob movement and how to pull only one group at once.

Seek for skills that prevent damage, not only on your monks but also on other professions. A minion master is always good, adds both damage and 'cannon fodder'. But an damage earth ele with one or two wards (keep players in them though) is also a good choice.
But remember, stuff that died cannot do damage anymore. Keep your team's focus on damage, not on defense. Only a few areas need additional defense or a specific team build (Rotscale is annoying to kill with a 'regular' build).

Also remember that sabway/discordway are not easily played by human players. Try to understand how they work and what you can do and cannot do with human players to make them work (are you on TS/Vent for a Discord Spike, can the 'healer' play both healer and damage dealer at the same time).

Good luck, you will find out in a while that HM isn't that hard after all if you learn some of the basic mechanics of the game