On whether or not there are healing mechanics that work poorly in this setting....
On the minimal healing end, I've already mentioned Vagrant Story, which encourages behavior that is neither fun nor challenging (standing in a doorway for 5 minutes).
That is a pretty bad way to play VS, just saying <_< You should either be exploiting your low HP to absolutely destroy your opponents with fixed damage based on lost HP attack skill, be using the 3 MP Healing spell to heal back up (Outside of combat you get 1 MP every... 2 seconds I think it was) and if you are REALLY bothered by it you should be chomping on one of multitudes of items you have.
The worst offender is RISK reduction, which if you have capped out and want to reduce it, without using an item you pretty much have to sit still for 100 seconds which is a big joke. If you need to run around to reduce RISK during a boss fight then you have made a mistake at RISK management, which is a fairly big factor in the game play (And is where you should be spending your risk reduction items rather than times where you can wait for it to drop).
VS has some pretty glaring issues though in terms of communicating the complex systems to the player. Most of it is right there in the documentation and it is all there in the game, buuuuuuut it is pretty incomprehensible, it is written by people that know the system for people that know the system. It is layer upon layer of complex systems in a game that certainly doesn't present a challenge that matches it (It is at heart a fairly easy game to break with a ton of situations that can be handled by just playing defensively and slowly chipping thigns to death, which is tedious and not difficult).
If you want an example of the lack of ability to communicate with the player, then healing is actually a pretty good example. The best situation to heal in is one where you have your weapons drawn, but don't have a shield equipped and have capped out RISK. Your hit rate drops as your RISK increases, your critical hit rate goes up, but at the cost of all incoming spells and attacks increasing in power. When you don't have your weapon drawn you don't gain the INT bonus from it, so drawing your weapon will make your healing stronger, but if you have a shield equipped because Heal is a Light spell you are going to have more Light resistance so your healing is going to be weaker (unless you have a shield that is weak to light, which is pretty hard to do because casting Heal will have a chance of increasing your Light resist each time). When you have high Risk you cast heal on yourself and because you are being targetted by a spel the magnitude of its power increases, so the magnitude of healing when just spammed regularly to when you use it in the most optimal conditions can increase by a magnitude of about 3 times.
Convoluted as all fuck and effectively a fairly elegant system that is put in place completely under the players control since the only thing that effects RISK is handled by the player (there is no enemy attacks that add to your RISK). Communicating that to the player? Now that is a bitch.
But anyway, your scaling for healing on extreme levels of difficulty are going to vary a great deal. If player healing is to good it isn't an extreme difficulty level, if it is to weak then it is pointless and your strategy trends more to avoidance, walling or disabling the enemy instead of healing. It can quite easilly be used as the dial you turn to control difficulty levels by increasing damage incoming and thoroughly reducing healing, which is why you see it as the most commonly used difficulty level tweaker in FPS games, classically in the aforementioned DOOM.
From memory that series also brought an interesting twist to that in Doom 3 where they set sliding levels of effective max HP. You could always get up to 100 HP (I think? Maybe 200), but on the harder difficulty levels it would constantly be being drained back to a certain point (Alex would remember, I think Nightmare had you running around at 50 health). So you could keep the effectiveness of healing about the same, but by limiting supply you could up the difficulty and have a controlling factor in play that would keep the expected upper threshhold value that you had to balance difficulty around in play. Of course Doom 3 had a far easier Nightmare than Doom 1 and 2, so, such is life.
RE: WoW and the giving people even footing to see the final boss. The design may not play to everyone, but as a mass marketted product, placing incredibly high focus on content that next to none of your audience can see is not only a pretty asinine and insane business model I also don't see it as being terribly fulfilling to the kinds of creators that are happy working in a mass marketted environment. Crazy difficulty like that has a place, it isn't really a healthy design space to be in a multibillion dollar situation. The balance requirements of that level of play are just far to fine a line to walk and at that point you aren't dealing with the kind of money where you can just fuck it up and take the loss once and go back to the drawing board. You drastically need to be looking at long term sustainability.
Alternately, a game that you play for months at a time and have no hope of acheiving anything in whatsoever other than serving as the boot that other people stand on the shoulders of so that they can reach great glory? Fuck that. That is not special or deserving of any hype or additional money, let alone any money at all. That is how elitist hardcore raiding was working in WoW. You essentially had entire factions on servers essentially serving as fuel for recruits and resources for the top few raiding guilds. They weren't necessarilly especially good at the game itself so much as good at the social metagame on the realm forums and general epeenery. And that was where a ludicrously out of proportion percent of the development budget was going. At that, WoW was a horrible game. Why would you spend any fucking money on that when you could be doing it in EVE and get far greater e-fame and e-peen?
As is? WoW has come a long way by dropping that bullshit, it has actually evolved far more from its classic Everquest roots for it. Epics for casuals and blah blah blah, but it actually gave MMOs their Mario in a genre completely dominated by Mega Man 1s. This is a game that tons of people can pick up and play without having to sink untold hours into just to get anywhere like you do for other MMOs. That is FAR from a bad or unhealthy thing for the industry or the genre.
Unfortunately by very nature of MMOs the best way to make a Lunatic mode is to A) have tedium and B) have PVP. A) because by nature you are going to have situations where people are abusing the system by using other people, so to make it something that is incredibly restrictive you need to limit resources or access by setting the hurdles completely out of reach of all but a few and B) well B) because that is quite easilly the best way to make A) happen. Add in greifing opportunities and situations where people can set up their own little gangs and protection rackets? More grind to fuel the fires.
If you just make the fights incredibly difficult and have the access to the sections not be the hard thing you end up in the situation WoW is in at the moment where because everyone can raid, holy shit people can actually practice and the community generally improves at the game, so you get complex battles that are juggling 5 or 6 situations at once that people have had to divine ways to react in worst case scenarios to get through the fight and then people yaawwwwwwwwwn raiding is so easy these days this game is lame. Epics for casuals ruined everything! they cry. The reality of the situation is that raiding has become pretty complex and you know, people have just been playing the game for years so GASP there is a fairly large pool of at least competent people playing the game, so the difficulty becomes less finding 40 people who know to get out of the fire or to not blow everyone up and kill the raid and more finding 10 or 25 people that can react to 5 or 6 different things which can kill them that would cause a raid wipe.
So... Tedium can work as a hard mode in some genres. It just has to be a worthless genre built entirely around horrible horrible design.
Also I guess since on the WoW train. The system of fights there is actually one that has enemy healing being a fairly effective combat issue. Healing is used to extend the bosses effective durability in most cases there (or to punish mistakes, commonly both), that is because you are almost always working against a timer on the boss. If the boss is going to explode in 4 minutes and it is going to take you 5 to kill it because it healed? You have succeeded in having a way to make boss healing more meaningful and less of a turn to exploit either offensively or to regroup.