HEY! I have an objection to your argument! I can't believe how often people say that, but they don't know what they are talking about!!!
how dare you say monks suck!
my first char ever was a monk20, and he was freakin immortal. his flurry may not have oneshotted mobs, but he wouldn't ever die. the GM had to make a rogue/assassin to kill him, casting true strike before the death attack to overcome my 53 AC (at lvl 20)... and even then, he only died cause i kept rolling ones on the fortitude save. people severely underestimate the tankitude of the monk, as the insane AC, über saves, annoying as hell spell resistance, immunities and the ability to self-heal.
as for your arguments pertaining to 4e, I find no flaws
Your entire argument is false. Time to be educated.
First of all, AC 53 at level 20 is not high. It's not even that good. In fact, just about anything that cares about melee will hit you on a '2'. The fact your DM needed True Strike to get through this instead of picking a CR 20 creature at random out of the MM that isn't the Balor or Pit Fiend (casters, who don't care about AC at all instead of just 95% of the time) is a testament to his extreme incompetence, not in any way representative of you being remotely durable or useful.
Second, death attack is blocked by the same things sneak attack is. The fact you were not simply immune outright is a testament to your failure as a player. Note this is also a failing of the Monk, as they have a much harder time getting immunity than anyone else. They still can though, which is why it is also your fault.
Third, in addition to your AC in fact being trivial which is already covered, there are additional failings in your statement. They do not have 'uber saves'. They don't even have very good saves. See, to have uber saves you need to have a good save progression, your primary stat boosting those saves, and be a caster so you can further them boost them. Instead you just have the good progression, but tied to a secondary stat and are not a caster - so your saves are half decent at best. Maybe, if you're lucky your so called good saves will be better than a caster's bad save by one point or something. Otherwise you completely and utterly fail at getting good saves. SR? Are you actually serious? SR = level + 10 is a total joke. If it ever
blocks any spell
you should consider yourself extremely fortunate you're fighting an incompetent caster - you might actually survive the entirety of round 1.
Immunities? To what? Disease and poison, and that's it. Both things that are only level appropriate at low levels due to trivial save DCs and easily dealt with via means also level appropriate at those levels... except you get immunity to disease at level 5, when it's no longer relevant and immunity to poison at level 11, when any real character auto passes nearly every poison save they will ever encounter.
Lastly, their self healing is fucking 2 points per fucking Monk level a day, and they don't even get it until level 7.
Monk: Look at me, I might actually negate a single attack from a single foe if I burn a round on it once a day! I'm so awesome!
Real character: Why do we bring this clown along again?
Other real character: The lulz. And he's a cheaper pack mule while we save up for a Bag of Holding. Shame about him leeching the XP though.