I've been playing WoW (World of Warcraft) for a couple of months now. I currently have a level 31 Tauren Druid (Hotan), and a level 24 Forsaken Priest (Gleb).
I logged in with Gleb the other day only to find a lvl 24 bear munching on my decaying skull. "Oh Yeah! The server crashed last time I was on." Nothing a little power word shield, can't fix. I ignore the bear and run back to town.
Back in Tarren Mill I find the most wonderful surprise, no not the "Hallow's End" celebration, though I think it's cool to see all of the decorations and go trick-or-treating. I really want to do the quests for it, so I need to go visit the wicker man at undercity. At Tarren Mill there was this big PvP battle going on, probably 20+ Horde adn more than that of Alliance duking it out. Most of the leet dood hardcore players will complain if you join something like this at lvl 24. I've heard a bit of that.
"We're going to lose because our whole team is only like level 22 man..."
"Don't come to BG until your higher level noob..."
Anyways (by the way I'm told that isn't a word...I don't care.), I'm a priest I can ALWAYS contribute to PvP. If my shield keeps a warrior alive through just one more hit, or my heals preseve the real fighters lives for just a few more seconds, that could mean the difference between who kills who.
Healers are not the only folk who can contribute at lower than cap level. Have you ever been in a battle and wished there was some way to get those pesky rogues to come out of hiding so you can clobber them? I know of no better bait than an easy kill and low level characters make for the easiest kills. Many have said "Just one more hit and I would have had him." Well, it's not unheard of for us low level characters to do upwords of 100+ dmg. I know that doesn't sound like much to the level 60s, but just that much may change the outcome of the battle.
One exception I know of where there is good argument for low level characters to not be involved is the battlegrounds (BG). Everyone needs to be atop contributor to win, and the number of participants is limited. So a level 22 priest trying to do much in warsong gulch really is a joke (been there), but a level 29 character is a dominant predetor in BG. Hey 29 is still low level in the grand scheme of things, but when BG are designated for level ranges, 29 is king.