In a straight up white room simulation, we can calculate the survival odds of a party based on their stats and the monster stats to determine if the encounter is overly deadly. Lets say we run the simulated combat ten times and the party has at best a 30% chance to win the fight.
In actual play, the party does a good job scouting, recognizes the threat, a formulates a plan to deal with it. They could prepare a nasty trap, lead the monster into it and kill it with relative ease. They may locate another monster and lead it to the problem monster, start a fight then mop up the winner. The circumstances of their approach are everything in this case. A probable TPK is turned into a solid victory based on encounter circumstances being under the players' control.
In order for the players to be successful in scouting, etc., it requires the cooperation of the DM. If he makes the DCs too difficult, the group might be back at the 30% success level. If he makes it too easy, then the PCs are getting easy XP under the illusion that the PC actions actually mattered. But in reality, the DM was helping.
The fact is that if the DM sets up the 30% chance to win encounter and the players do NOT come up with a good solution, or even have bad dice rolls, or even did not figure out that they needed to come up with a non-direct fight solution, and the DM has a punitive Raise Dead, he's screwing over his players. He's the one who set up the encounter and he's the one who set the DCs for a workaround solution.
To me, that's bad DMing. Not the 30% encounter, but the fact that the DM is blaming the players for not being good enough on a given day to figure out a solution to his mega-problem and on top of that, he is penalizing the players for failing and having PCs die. Sorry, that's lame. It does not matter how one plays the game, sets up the encounter, or how well the players figure out a way around it. Combat will occur, cold dice rolls will occur, and PCs will die sooner or later in most games. Penalizing the players for it when it happens and saying that it is their fault because they did not come up with a good enough solution and the DM not taking partial responsibility for the outcome is weak.
There's nothing wrong with PC death. There's nothing wrong with players making mistakes. There's something wrong when the DM does not understand that players are at his table to have fun and a lot of that fun comes through the cooperative and continuing storyline. The latter part of this is the word "continuing". When the DM tries to harshly modify the characters (e.g. giving them mental quirks, or lowering their ability scores, or punishing them with resurrection, or whatever), some players will wonder what the point is. Why is this DM being a jerk over this?
Some of the least satisfying games I have ever been in have been ones where some PCs die and the players are discouraged by the DM from getting their PC back. The story just, for all intents and purposes, stopped. Sure, the campaign might have continued, but the story stopped because Regnar is no longer part of it. Meh. There's nothing wrong with the players having to strive to get Regnar back, but punishing the players and not comprehending that the DM is also responsible for Regnar's death is where I draw the line. A DM who cannot figure that out, maybe not the DM for me.