DnD 4E Rules I Don’t Like [I]: Flanking
The 4E rules on flanking are very similar to the 3.x rules that I didn’t like. The rules are quite clear (PHB 285): “Combat Advantage: You have combat advantage … against an enemy you flank.” [emphasis mine]. I hate this because it doesn’t make any sense that if a monster is flanked by two PCs that a third PC attacking the monster should not also have Combat Advantage over the monster. If you are distracted by two foes on opposite sides of you adding a third vector of attack should be harder not easier to defend against.
My rule change would be to add a new condition to the list of conditions on page 277 of the PHB:
* You grant combat advantage
You would gain the Flanked condition under the same rules on page 285 of the PHB, but once flanked anyone attacking you would have combat advantage.
This rule change will help encourage parties (and nasty DMs) to use the tactical roles better. If two melee beaters maneuver to flank (perhaps with assistance from a leader), not only will they have an easier time hitting, but the fragile ranged specialists (e.g., bow wielding ranger, warlock, or wizard) will be able to take advantage of the opponents compromised position.