This is Bob.
I'm about to start a new group, and with it come the regular issues that begin a new campaign, especially with new players. Most will try to optimize self-sufficient, front-line assaulters that rely on eliminating the enemy through sheer force. There will be very little cooperation, and probably one guy will be issuing all the orders, which the others will ignore. There will be much blundering into rooms in search of ill-gotten treasures, and I thoroughly anticipate belligerence towards obviously-superior enemies. Most players don't believe I could ever throw anything at them they can't take. I do.
Let's discuss the next step in tactics, which will enable players to take on far superior forces. The next step is cooperation, or planning around your team mates. I'd like to start with an example, followed by more examples.
1. The Half-Orc Rogue and his Never-Hitting Warlord friend: The Half-Orc has a mace, and is optimized for doing damage. The Warlord uses only abilities that allow his allies to strike better and harder. The result is very often a target that must roll to save against death.
2. The Infernal Warlock and the Sorcerer/Wizard: The Wizard or Sorcerer uses an attack that creates a minimally-damaging zone, such as Storm Pillar (wizard) or Blazing Starfall (sorcerer) within movement range of the warlock. The warlock then attacks a target, using Hellish Rebuke. If it hits, the warlock runs through the prepared, damaging area, forcing Hellish Rebuke's secondary attack to activate.
3. The Warlock and the Wizard, Level 5: Indelible pull! The Wizard uses Visions of Avarice, pulling all enemies towards a central point, doing no damage in and of itself... but his warlock friend has unleashed Hunger of Hadar at the center of the Visions of Avarice, forcing the enemies to return again and again to a painful, dark death.
4. The Avenger and his Defender: The Avenger has maximized himself for resisting opportunity attacks at high speed. After the Fighter is in position at the front, the Avenger runs through his enemies' threatened zones, provoking opportunity attacks. The Fighter ally at the front is equipped with a mordenkrad and the Headman's Chop feat, along with whichever feat lets him knock enemies prone, to maximize on this inverting circumstance.
5. The Shaman Ambush: A party may consist entirely of Shamans and will not only be none the worse for the wear, but will be much more powerful than a normally-balanced group. The fact that shamans can summon their animal allies within 20 squares (cubes, really, meaning vertical positioning is useful as well), in conjunction with the backgrounds that Wizards of The Coast offers, allows your shamans to add to their class skills: most importantly in this circumstance, STEALTH. Equip your shamans with whatever materials and equipment are needed to be stealthy. Add to their stealth first and foremost. Give them the feat that adds +2 to all the defenses of their Spirit Companions. You will always get surprise rounds, and you will minimize damage to your shamans by keeping them hidden. The Spirit Companions do all the work. Consequently, it makes the most sense to use only Panther shamans for such an attack.
5.1. The Shaman Ambush, Amplified: With at least one Panther Shaman and a Shaper Psion, use the psion's Static Mote power to pin enemies while spectral panthers annihilate the enemies. Make sure that your psion takes the Discipline Adept feat, to ensure distancing from himself and the enemy, while focusing on utility powers that grant him a stealthy approach. Take the "Arcane Agent" background for STEALTH as a class skill. This is an incredibly brutal combination that utilizes the doctrine of battle by proxy at its finest.
6. Psions: Such Great Heights: Psions (especially of the Shaper and Telekinetic sorts) are perniciously adept at moving things. The at-will Dimensional Scramble is among the most underutilized powers in the entire game. Simply put, it teleports enemies into the air, and they fall for extra damage. If they manage to save against the teleportation (on a roll of 10 or better) they still fall prone in their space. This is cruel, combined with various feats that frontline men can take to crush prone enemies...
Let's assume an ordinary yet optimum circumstance, in which 3 psions have elected a target to die. The first psion scrambles an enemy (assuming a failed save versus the teleportation) outside of a burst 3 (being a cube of dimensions 3x3x3, has been sagely placed in the air one cube above the target) the target may be teleported up, vertically at an altitude of 4 (the ground being altitude 1, as it must be measured cubically), whereupon he who has held initiative for such a circumstance also engages his Dimensional Scramble, and places the target at altitude 7 (assuming a second failed save), whereupon the third follows suit, placing the target at altitude 10. If a fourth psion is present, and in this scenario we assume that the Discipline of Shaped Consciousness has not been manifested in any way ABOVE the users, limiting the vertical range to a nominal 10 for the powers, the scrambling still may eject the target at an altitude of 12, with 10 being the focus of the burst. Altitude 12 - Altitude 1 (ground) = 11. For every 10 feet (2 cubes) a medium-sized creature falls, it takes +1D10 damage. In a single turn, our decisive attack has netted the psions a staggering 4D6 + cumulative Int modifiers (probably +5 each, so 20?) + 10D10 damage. Minimum damage will be 4+20+10=34 damage, enough to kill many first-level creatures or characters; and a maximum damage of 24+20+100=144 damage, enough to displace brutes of upper-heroic tier proportions...
In one turn.
7. The Cadre of Spell-Slinging Wizards: Magic Missile is a daft thing. It auto-hits. It auto-hits ANYTHING, regardless of level or armor class. Damage resistance is the only way to obviate Magic Missile, and not much ignores force damage. It takes about 50 level-1 wizards, all equipped with Magic Missile and Wizard's Spellfury (or something like that) as a daily power and two rounds to kill Orcus himself, while getting none of themselves killed... under optimal circumstances.
I hope these examples help you consider building your characters as a team. Before you pick that piddly +1 to fire damage feat, think to yourself, "What can I do to let my allies double or triple the overall damage of this round?"
I think you may be surprised. Some feats that sounded like utter crap are actually overpowered in the correct circumstances. Of course, for all the advanced tactics explored here, there are countermeasures. Rarely will you get just the right scenario... but when you do, exploit it.