Yeah... coming from an mmo is a completely different head space than pen and paper rpgs. Sounds like your group is fine. I'd still try and convince the group to invest in some more shared healing items, but I wouldn't worry too much about filling in those "missing" roles. Wish I had mentioned it in my first post, but the most important role to fill (in my opinion) is the one where you and your fellow players are having fun. Most of the stories I hear/tell about D&D games involve the theme "Oh crap, things went south and then we survived anyways."
I agree Greenfield, you guys are missing Trapfinding; which can be a serious problem depending upon the DM and/or adventure you are running. I would however, suggest the Scout (
Complete Adventure) instead. While their bonus precision damage (skirmish) is less useful than the rogues (usually limited to once per round and you have to move at least 10ft) they do provide the same amount of skill points and have a d8 hit die instead of a d6. In addition, if you're willing to take at least 3 levels of scout, you can pick up the Swift Hunter feat (
Complete Scoundrel; pg 81) which allows you to count your Scout and Ranger levels as one for your skirmish and favored enemy progression as well as a few extra bits. A Scout 3 / Ranger 4 would have their 2nd favored enemy and skirmish (+2d6, +2AC).
Since you seem to like the idea of a skill monkey, you may wish to look at
Complete Scoundrel's Skill Tricks (chart pg 83). For the price of 2 skill points and meeting the prerequisite, you gain access to a pseudo feat. You can have a maximum of half your character level in skill tricks.
Collector of Stories would definitely assist in identify what the heck your fighting.
There are also scattered through a few books and dragon magazines (
here's a list), alternate class features that replace ones the base class provides. If you do go Rogue (or Scout)/Ranger and want to completely skip spellcasting;
Complete Champion and
Complete Warrior have your back. Champion grants you a bonus feat from a limited, but useful list at ranger levels 4, 8 and 14. Warrior grants a bag of different useful abilities, though non will come online if your multiclassing until you gain some levels. If you do multiclass and take scout, the land speed bonuses stack.