Which role is most consequential in a party?

This is something that I have been thinking about for quite some time, so I thought I'd write about it here. I'll tell you right now that my group experience is largely limited to five-mans, and its those experiences I'll be basing this dissertation on. For the record, I am, of course, referring to the roles of tank, DPS, and healer.

When I first thought about this issue, I looked at the consequences of one member of the party not pulling their weight. If a tank doesn't pull his weight, then the enemies go off to attack other members of the party, killing them. A fantastic healer could make up for this kind of fault, but only so much so. If the DPS don't pull their weight, the enemies won't die fast enough, which can be bad if they have an enrage timer, but otherwise it is only bad inasmuch as the healer might run out of mana trying to heal the tank. If the healer doesn't pull his weight, everyone dies, plain and simple. These are all very extreme cases, though, so these are not the end-all-be-all determinations.

Another thing one needs to consider is how much a good person filling each role can improve a run or save a run gone sour. When a group has a good tank, he can cause enough threat that the DPS can go all out and kill things faster, thus the run will be over more quickly. If the DPS get a little overzealous in their damage, the tank can use taunt liberally to make up for that fact to an extent. If the healer isn't so great, he can use his defensive cooldowns judiciously to make up for that fact as well. In short, a good tank can make a good run fantastic and can do some things to improve a bad run.

While good DPS is worth their weight in gold, I'd say they can't do much to make a run better if it goes sour. Sure, some can be emergency tanks or emergency healers, but if the tank and healer just aren't doing their job, there isn't much the DPS can do to make up for that fact. Granted, smart DPS can make a run much more smooth. Every time I see a DPS actually follow the kill order, not use an AoE attack on a pull with two or three enemies, watch his threat, and get out of the fire, I know the run is going to go much more quickly. So, in summary, good DPS can't do much to make a bad run good, but they can do a lot to make a good run great.

Which leaves us with the healer. If a run is already going well, the healer's job certainly becomes easier, but he can't do much to make the run better, with one exception. If a group vastly out-gears a dungeon, they can ignore the boss tactics and simply burn the boss down. However, doing this means the group will take a lot more damage, and who needs to heal that damage? This kind of thing requires active communication between group members, but I can say from personal experience that if you make that communication, your runs can be made faster. And if the group doesn't know what they are doing? Then the healer can pull out the big guns and heal them harder. Yes, there is a sort of ceiling on how much healing per a second a healer can put out, but you'd be amazed what a good healer can do when everything goes wrong. So, in short, a good healer can make a good run faster and a bad run salvageable.

So where does this leave us? A bad healer can screw over a run the most, the healer and tank tie for saving a run gone bad, and good tank can make a good run even better. It seems like the healer and tank are equally consequential then. I suppose it just matters where the party is in terms of average skill. The lower they get on the scale, the more consequential the healer becomes, whereas the higher they get on the scale, the more consequential the tank becomes. Seems about right to me.