yeah, try playing the freebie adventure, by yourself or with pals, not to "Play" but to grasp the changes

4th ed is less about simulation and more about dynamism and team play.
Pcs can really work off each other's powers and tactics
this is most seen by the Warlord class, which is FINALLY a good representation of say, an officer or NCO, or heroic leader like Belesarius, John Paul Jones etc
the warlord doesn't do as much damage himself, but, he has lots of ways he can boost the party's attacks, defences, and "heal" them by spurring them on again etc.
Hit points ain't "health" more about "will to fight" fatigue etc, so the warlord rallies and drives his friends on, points out openings and weak spots etc.
more in the party the more the warlord's powers shine.
Wizard's generally the one you want with high initiative. rather thanbe a mega-killer and totlaly dominating most parties liek they used to, wizards are more about totlaly ruining the enemies' plans, ability to get cloe to the party, slaughtering tons of minions because he is one of the few with lots of Area of Effect powers.
a classic example of this is the "Visions of Avarice" spell. when triggered, it "Pulls" enemies towards a square, where they see an illusion of treasure.
doens't do damage, but it totally screws up the enemy's ability to overwhelm the party!
While I initially loved 3rd ed, the complexity soon became a nightmare for me as DM :/
4th ed's designed to keep it MUCH simpler to design critters/ecounter,s but actually let them do more of NOTE int he game
for example, say a dragon had in 3rd ed 24 spells and abilities...it would use only a few in most games. so why have so many in the first place?
Better to have fewer, but that let it do more useful thingsin combat, that are easy for the DM to track, like daze close up attackers, Daze = can't do opportunity attacks, so the dragon could move away etc.
Another thing is the removal of stat affecting powers/effects and level drains
those were a nightmare to calculate all the time!
isntead, you may get "weakness", your attacks do half damage. Which is MUCH easier to calculate and just as damn scary in a fight.
the enemy can get just as much milage out of the better tactical abilities as the party can, so it behoves the Players to co-operate even more, and makes the "soloing kill junky" PC a warm soggy marshmallow

rogues/rangers cna sitll jump out of shadows and slaughter guards very effectively, ESPECIALLY because of the minion rules, but you aint jumping a room full of 'em and getting away with it if yer silly enough to just stand there.
movement/tactics is king. just like real fights, I find this MORE simulationist than simulating critters in detial as per PCs.
3rd ed added more use of movement/tactics, but 4th ed WAY takes it up.
positioning by using pushes (away), pulls (towards) and slides (anyway you want) really change the games dynamicson the table

I used to get annoyed with the "stand there and whack-a-rat on each other" style of combats before, you didnt get much beyond a bullrush, charge, trip or disarm and those had problems (taking up an action etc) now, you get the movement AND the normal or better damage in an attack.
Melee fighters, because of the movement/tactical stuff, really shine at last

it's not just "whack whack whack"
the fighter pins enemies down, he's right in their faces, threatening them all the time, if they don't attack him and go for the wizard instead, they suffer attack penalties or the fighter may get free attacks on them etc.
again that's more simulationist than before. yeah ignoring the gladiator to stab the scholar beside him is NOT a good idea, as the gladiator is gonna take that opening and push his gladius where the sun don't shine!
healing, buffing and tactical movement of foes and allies usually are PART of an attack or such, now, so you don't lose out for being more tactical and saavy in a fight

the cleric is NOT reduced to being the party's "duct tape bandaid commando", lol.
minion rule is very good, not just for allowing more combatants, but also for things where, as said, the guard on watch is a total mook, one shot
should be a kill, but in other editions had the tendency to not die so easy, backstab or not
it took me a while to "grokk" the differences, as it is quite a shift in thoughts, but it is so good especially for a DM
(simulationist/gamist, meh I use 'em my way, others use them their way of meaning

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