Mogtalk interview with yoshi p

[Zojha]

Nerfing healers simply is going to make it impossible to fix mistakes.

That's partially the point.

When a healer can easily fix a mistake and a piece of content is not supposed to allow for many mistakes, then you need to prevent healers from being able to fix them. And instant-wipe is the hard form of that, instant death the soft form, because they bypass heals and only allow raises, which are more costly. Those are the two most common, but any measure you take will have to be aimed at healers here.

That has no bearing on how many mistakes a content may allow or how hard a content is. Even if you have no healers at all, a content may allow a lot of mistakes when mistakes simply deal very little damage.
Imagine you have 1000 HP, no means to restore it and the boss only deals damage if you make a mistake. At 1000 damage, you cannot make a mistake, at 500 damage you can make one, at 100 damage you can make nine and at 1 damage you can make a thousand mistakes (minus one).
Now imagine you have 1000 HP and your healer can restore a total of 5000 HP, then he goes OOM and cannot fix anymore mistakes. How many mistakes can you make now? With 1000 damage, you still can't make any. At 500 damage, you can make 11. At 100 damage, you can make 59. At 1 damage, you can make 5999.
Tuning with healers is actually a lot more iffy than without, especially with mana regeneration and all that jazz in the mix.

Another thing is that the weaker healers are, the less damage you can give your encounters, which in turn makes the party rely on them less. Example:
You have a health pool of 30k. The encounter assumes that your healer will heal you for 10k every GCD and thus deals 10k damage every GCD. How long do you survive without a healer? 2 GCDs.
Now assume the encounter assumes your healer will only heal 2k every GCD and appropriately lower the damage to 2k a GCD. How long do you survive now? 14 GCDs.
And if the damage is only 2k and healers can still heal for 10k? Then the healer is just going to be inactive for 4 GCDs. That's expert roulette.
This is actually why VIT accessories are so completely worthless - Like 99% of your health as tank comes from the healer, not your base health pool. There's no point increasing it, it doesn't make you survive any longer, you'll have long hit enrage before the healers run dry and your VIT gets its 1 autoattack of fame.

The stronger healers are, the faster health is going to move in either direction. You can see that in the first example: If you want to allow roughly 10 mistakes, the scenario without healers is going to take chunks of about 10% of your health bar for each. The scenario with healers instead takes about half of your health bar with every mistake for the same effect.

This game is pretty extreme on healer power and damage thus very spiky and burst heavy. It's similar in PvP, where healers make damage that doesn't come in bursts trivial and shift the meta to focused CC and burst.

That said, though... I must admit I also can't imagine the game working if healing (and thus encounter design) got re-designed. Not because of anything healer related, but because there'd be less group DPS to compensate for Yoshida's completely outlandish expectations towards DPS players.