4e cant be deadlier than 3e if they removed the save or die effects, plus the rules for going negative arent the hard -10 anymore, correct?
Monsters might be more durable, but that doesnt make them deadlier.
In some ways, it's less deadly; in other ways, your character can still get REALLY screwed over, really quick. How, one might ask?
1) Falling damage does almost twice the damage it used to; in fact, THERE'S NO 20 DICE CAP like in previous editions of D&D. Characters, actually, have fewer hit points per level than their previous counterparts; 20th level characters with a 20 CON will have around 130 to 150 hit points, compared to clerics, rangers, fighters, barbarians, etc. who had normally 120 to 200 hit points or even higher at those levels.
2) Monsters even moreso than before have special abilities that make you do things you don't want to do, now - from sliding you into harm's way on a battlefield, to interposing your body as a shield versus OTHERs in your party, to even killing you and making you rise as an undead to fight your party.
3) Monsters still petrify you, disease you, disintegrate you, etc. -- but in two saves instead of one.
The biggest change is in hit points now -- monsters usually have to rip through your hit points now to destroy you in some fashion, instead of one-shot killing you. The other effects are a TWO-shot kill instead of a one-shot kill, to give you a "fair chance." So if one measures deadliness by one die roll standing between you and a raise dead, then yeah, they're largely removed that. But as far as deadliness is concerned, 4e generally instead of killing you
makes you watch yourself die.
Instead of
"the medusa kills you" it's
"AHHH! The Kruthiks are ripping me to shreds! GET THEM OFF!!!
Instead of being a target of hold person and then your throat slit for instant death, it's "hold still, though your brains are on my hammer, I've got to hit you again.... oh, your skull broke? Sorry, I'll get you with the next hit"... until you hit that -bloodied value.
On the other hand, if you DON'T die, then it's ridiculously easy to heal up to full... but by only a few days compared to 3rd edition. A 3e fighter can heal up from -9 to completely healthy inside of something like 3 to 5 days without a stitch of magic, which a lot of people tend to forget.