Random Powers and Feat Scaling
Some At-Will powers and feats don't scale with level, such as the Paladin's Bolstering Strike and some feats, making them useless at higher tiers. There are too many of these powers and feats to list individually, so the general rule if an at-will or feat doesn't scale, give it a +3 bonus at 11th tier and a +6 bonus at epic tier. Do not ever make feats that grant a bonus to attack rolls or defenses scale.
Feats: Weapon and Element Feats
Remove all stat requirements for all weapon-related feats. Yes, all of them. Hammer feats no longer require a high Constitution, blades don't require a high Dexterity, polearms a high Wisdom, and so on. This also includes the critical hit feats in epic tier. Wizards didn't have stat requirements for further weapon feats, so why should these feats? Why can't a paladin or a swordmage be good with the very blades that iconic to those classes? Also, improve the damage bonus from Weapon Focus to +2 at heroic, +3 at paragon, and +4 at epic.
This also applies to all the element-styled feats in the first Player's Handbook, such as Burning Radiance. Those stat mods just make what's already a questionable feat worse. Improve the damage of all those feats to +2 at heroic, +3 at paragon, and +4 at epic. Those bonuses will make people actually want to take the feats and change their style to fit using one (or two) elements, not the pitiful +1's, 2's and 3's of the old feats! Players need to feel iconic with their specialties, and a +1 to damage does not do that.
For those of you who are looking at these changes and ask "But what about game balance, Spyder?" Please remember these are feat bonuses, so you can't have the bonus from Weapon Focus and the bonus from Burning Radiance apply to the same power.
Multi-classing is... tricky... in 4th edition. Most people don't attempt it because of the huge feat investment that it takes to only swap out powers. The solution?
Take away all the power swap feats. But just having one feat for something that powerful is too much, however. There should be one more power that allows you to swap out one encounter, one daily, and one utility power from your multi-class class. But all things come at a price to stay balanced, and this houserule has that too. You'll need to remove the bonus trained skill from the multiclass feats. Those feats are now good and do exactly what they're supposed to do without overshadowing the Skill Training feats.