But, yes, statistically with with a 50/50 hit chance you /will/ get runs of 3 or 4 (or more) frustrating misses in a row often enough to notice. This is no big deal when your the leader who's also healing and passing out bonuses, or the defender who's still marking and standing up to the enemy, or the wizard or ranger who's making more than one attack roll per turn. But, if your main claim to glory is hitting the other guy (striker), and you miss the other guy 4 rounds in a row in a six round battle, your pride is going to be smarting a bit.
At the same time, strikers have a better chance of hitting.
The ranger has multiple attacks, giving a better chance of at least landing one (and getting the resulting quarry damage). The rogue can go with a dagger to increase accuracy, not to mention he wants combat advantage anyway, and has some weapon attacks against non-AC defences. Then there is the warlock with tons of attacks against Will, one of the lowest defenses on average for monsters. Finally you have the barbarian who can constantly charge to get that extra +1.
Prime shot for the ranged attacks, the mobility to help with flanking, and that's not even counting the beastmaster ranger's "pet to flank with" class feature.
In the game I DM, the Rogue rarely misses when she has combat advantage (which she rarely doesn't have, unless it's a situation such as a large monster, in tight quarters which make it difficult to flank). The warlock will still miss on occaision, but Sacrifice of Caiphon from Dungeon Magazine gives him a bit of reprieve from that idea.
Ultimately, it's up to the DM to figure out what is right for their players. The ability to go with lower level monsters, and just including more of them, is an option to increase hit rates. With a tactical group able to constantly supply each other with bonuses to their accuracy, like combat advantage, leader-based bonuses and such, can be challenged by having them go against higher level creatures, soldiers and the like to be able to make things more challenging.
While lowering monster defences would make it less frustrating for players of an "average" class (one without a built in bonus) AND a +2 weapon AND a non-maxed out attack stat (maybe without a racial bonus), it would make it way too easy for people that take every bonus they have, and then getting assists from the rest of the party become moot.
There has to be a balancing act between making it possible for players to make the kind of character they want to play, and rewarding smart choices (especially teamwork options). Optimization is one thing, but when a party has good tactics, even less than optimal characters can get a boost to their hit percentage, making the group greater than the sum of it's parts.