As an aside, I truly do believe that the overwhelming majority of issues that people have with 4e are due to the presentation of elements in 4e. If the writers had either backed off a bit in how they present the classes, or had included a few pages with each class on how easy it is to blur the lines between roles, it would have gone MILES towards defusing these misunderstandings.
While it's the case for many elements of 4e that a better presentation could clear up lots of problems, I think the problems people have with roles stems from a different issue, namely the fact that classes were defined by combat role rather than thematic niche. (Caveat: all of the following is observational data gathered from talking with players IRL and browsing forum threads and are being presented in that fashion; they do not necessarily represent the opinions of this poster.) To take a look at the martial classes for a moment, fighters in previous editions are the dudes in heavy armor who do fancy stuff with different weapons, paladins are the dudes on horseback who smite evil things, rangers are nature-y TWF/archer dudes with animal companions, barbarians are tough dudes that flip out and kill things and are really hard to kill themselves, and rogues are sneaky dudes who are fragile in stand-up combat but are great in ambush situations. So far, so good.
However, in previous editions, you could be a heavily-armored TWFer, a heavily-armored two-hander, a heavily-armored S&B guy, or whatever else, and your combat role would change based on that. In 3e, for instance, a 2HF fighter with Power Attack and Shock Trooper was more striker-y, a S&B fighter with Stand Still and Combat Reflexes was more defender-y, a TWFer with combat style feats and Cleave was more controller-y, and a fighter with Leadership and bunches of teamwork benefits was more leader-y. The common denominator there was the heavy armor, good health, and reliable damage, compared to a barbarian's lower armor and spiky damage or a ranger's lower health and situational damage or the like, allowing you to make your "strikers" more or less mobile, more or less resilient, etc. You could fill different roles better or worse, of course (e.g. the AD&D fighter with his followers could do leader-y a hell of a lot better than the 3e fighter, while losing out on controller-y-ness a bit thanks to HP bloat), but you could do it.
In 4e, they took everything martial characters could do and split them by combat role first, then schtick second--instead of deciding to be a weapon master or a sneaky guy or an archer and then choosing what combat niche to fill, you choose a role and then pick your schtick based on that. Essentially, 4e gave people the choice of role first, fighting style second (choose Defender over Striker -> choose between Str-based Great Weapon fighter or Dex-based Guardian fighter or TWF Tempest fighter; choose Striker over Defender -> choose between Str-based Brawny rogue or Dex-based Slayer fighter or TWF Two-Weapon ranger) when what a lot of people wanted to see was the reverse (choose TWF over Str/Dex single weapon -> choose between very Striker-y Two-Weapon ranger or Striker/Defender Tempest fighter; choose Str-based single weapon -> choose between very Striker-y Brawny rogue or very Defender-y Great Weapon fighter). If you wanted to have Combat Challenge
and wield two weapons, or Hunter's Quarry
and have a shield, you were out of luck; while you can easily make a striker-y Fighter by picking the right powers and such, the fact that you have to start with a Defender chassis and build it towards Striker stuff instead of having a blank slate and building up to the role of your choice rubs some people the wrong way because it sort of feels like you're working against the system rather than with it.
Because certain fighting styles were closely associated with certain roles (particularly with just PHB1) instead of being able to mix-and-match fighting styles with roles, people felt constrained by the dictation of roles, even though most of the roles are what they'd be doing anyway and the
actual problem was e.g. the lack of a heavily-armored TWFer option and not the fact that only rangers can TWF,
per se. If the PHB1 had had Ranger-scale TWF and archery options for Defenders and Fighter-scale two-handed and S&B options for Strikers right out of the gate, rather than trying to make a defender-y Striker because you wanted to be a TWF-based Defender or a striker-y Defender because you wanted to be a S&B Striker, I doubt roles would ever have been a problem, but instead a complaint along the lines of "I'd rather make my TWFers the mobile, sticky ones and the two-handers the straightforward, burst-damage ones" gets boiled down to a vague "Why do fighters have to be bodyguards!?!?"
Same thing with clerics being single-target damage dealers and buffers while wizards were multi-target damage dealers and debuffers with no option for the reverse: I doubt anyone disliked being labeled a Leader or Controller and getting the perks associated with those roles, but rather they wanted to choose between single target and AoE and between buffing and debuffing, not between single-target + buffing and AoE + debuffing, and so forth. That combinatorial aspect is why I'm hoping to see roles be defined by themes in 5e while schticks are defined by class, rather than having the two tied closely together.
