I'm giving Rangers a separate piece from the Big 4 as I believe the genesis of the "Striker/Defender" split in 4E lies with the Ranger rather than the Rogue which is where a lot of the discussion seems to have focused in the past.
Rangers - in 1E they could wear any armor, use any weapon, and had the saves and attack progression of a fighter. They had a d8 for hit points but they had 2 of them at 1st level, which actually made them tougher than the 1d10 fighter at the lowest levels. With an 18 Con you could start 1E AD&D as a 1st level ranger with 20 hit points! They also had tracking abilities and then added some minor spell capabilities at 8th level and up. Most interesting to this discussion, they also had a +1/level damage bonus against certain types of creatures - mainly humanoids/giants. This made them very handy in the G series adventures while merely about as good as a regular fighter in the D series modules. However, nowhere in the 1E writeup is the concept of rangers as lightly armored fighter, more mobile fighter, or more fragile fighter.
Role: Fighter substitute, especially if your DM runs a lot of outdoor adventures (tracking was usually a big player here as were some of the followers possible at higher levels) or if you thought regular fighters were boring. The tradeoffs were some stat minimums and some alignment restrictions, but this was not a heavy burden for most.
Complaints: Not many that I remember. Most people liked them just fine. Maybe that they end up looking a lot like fighters with a few powers added on but this was not a huge issue back at the time.
2E rather surprisingly added two-weapon fighting as the ranger's signature feature alongside tracking, but only in light armor, along with hiding and moving silently like a thief in some cases. Hit dice changed to d10's just like the fighter and paladin. The gradually increasing damage bonus against a list of creatures became a straight-up +4 to-hit vs a certain type of creature, period, ever. That was huge at lower levels so there was a temptation to take lower level creatures as the favored enemy, but it would be more important against things like Dragons which mostly came up later on, so this was a bit of a dilemma. So the 2E ranger ended up looking and playing somewhat different from his 1E form and set the template for what we see through 4E. I think it was the answer to a question that no one was asking, but it worked alright and gave rangers a somewhat different flavor than other fighter types.
3E Continued the 2E pattern - light armor, nature skills, outdoor thief skills, two-weapon fighting and minor magic ability. Bow specialization was added as an option as well. To some degree the Ranger became the "Skilled Fighter" at the cost of heavier armor. Favored enemies were now selected at several levels over the course of the adventuring career and the bonus was smaller but it switched back to a damage bonus, in addition to being a skill bonus The d8 Hit Die also made a return and so now we have a clear trend towards the future Striker:
- Light armor
- Lower hit points
- Bonus damage
- Increased attacks (two weapons or faster bow firing)
- Increased movement capabilities (Woodland Stride)
- Stealth capability
As a comparison 3E rogues use light armor, a d6 for hit dice and have a slower attack progression and no inherent two-weapon or archery skill, but they do get Sneak Attack damage, which is a conditional bonus that reaches +4d6 at 7th level and continues to increase every other level and have better stealth than a ranger.
4th edition simply completes this transformation. The Ranger is officially a Striker now, sacrificing defense for offense and really not looking much like a fighter, and you know what? I don't really mind. I played a 1E ranger all the way to 20th level over about 6 years and I liked it, but I don't mind the fighter-related subclass types branching out and finding a niche other than "specialer fighter". I don;t mind a class favoring offense over defense - you could do that with a 1E fighter by choosing whether to go with a shield or a two-handed weapon. If your iconic ranger is Robin hood, well, 4E rangers do Robin Hood pretty well. If your iconic ranger is Aragorn, well..that's a problem as the 1E ranger looks more like him to me.
What I don't like is that the Striker/Defender split being such a split. To me should be something reflected in the builds for an overarching "Fighter" class, ranging from slow heavily armored knight to swift lightly armored ranger rather than making it such a heavy break. I think that fighter type classes benefit from broader classes rather than narrower ones, unlike spellcasting classes. Quick, what's the difference between a fighter, a ranger, a barbarian, and a warden? Now what's the difference between a wizard, a warlock, an illusionist, and a shaman? Even a non-D&D player may have an idea on those last 4, but the first 4 seem a little more closely tied IMO.
Think I'm wrong? Look at leaders. Some are better at healing, some are better at buffing, some are better at granting actions to others, yet they are all controllers. How closely related is healing vs. "here's a +2 to will defense for a round" vs. "Take a free standard action"? Now how closely related is "I'm a tough heavily armored guy who hits people wit ha sword" vs. "I'm a fast lightly armored guy who hits people with a sword" vs "I'm a tough guy who gets really mad and hits people with a sword? Aren't they at least as closely tied together as what the "Leader" umbrella covers? I think they are.
So where does that lead? Are there really only 3 roles to be played - combatant, leader, and controller? Maybe. There were 4 archetypes in classic D&D but 4E is so different that the old archetypes no longer apply anyway unless you think the 1E Thief was a Striker class for some reason. It wasn't. Leader clearly comes from Cleric, Controller from Wizard (though it;s not as clear as some seem to think) and I think both Defender and Striker spring from the Fighter. Where does that leave the Thief? Let's look at it tomorrow.