The three tiers of Dungeons and Dragons 4th edition seem a little artificial in the context of a team of characters ascending from the merely heroic to godlike over a compressed time frame, especially if the campaign takes place over a compressed period of time. The strength of the Heroic, Paragon and Epic tiers is that it allows players to tell stories featuring characters of varying power levels. These stories have precedents in super hero comics that might help one think about play in the tiers.
When characters begin the game, they start as heroes with remarkable abilities and the will to change their world. On the other hand, they don’t have political influence or renown and might not be trusted by those they want to help. While they’re probably the toughest on the block, they aren’t the toughest in the city. This tier reminds me of the X-Men from Marvel Comics, especially during the mid to late 1980’s, when Professor Xavier and Jean Grey as the Phoenix weren’t around. Storm’s weather control was a little overpowering at times, but mostly they were a group that was on the run and got beat up a lot.
The Avengers remind me of a team in the paragon tier. These are characters that have been around the block; while Captain America (a warlord if I’ve ever seen one) doesn’t have any extra super powers, he can hold his own in any situation. Aside from a few exceptions (like Thor and Hercules), they aren’t at the epic power scale, but they can stand toe to toe with nearly everyone. They have fame, popularity, wealth and a lot of control of their own destiny. That’s what the Paragon should feel like in most D&D campaigns.
The epic tier isn’t something that Marvel Comics does very consistently. Doctor Strange and the Silver Surfer are good examples of that power level, but the best place to look is in DC comics. The Justice League of America is the team to look to when considering the epic tier. Superman, Wonder Woman, Batman, Green Lantern and the Flash… these characters defend the world and the galaxy on a regular basis. They are more than powerful heroes; they are heroes who symbolize power.