What P2P game beta have you played that they DON'T delete characters? Even the game you played most (Guild Wars) they deleted beta characters. Actually most P2P/B2P games that have open betas have a huge "Cleansing" of all characters. I remember MxO's end of beta. lol They literally killed everyone's characters by smooshing them with the big red eyes in the sky. Most epic beta ever, too bad the game did so poorly.
On that note, betas are for testing. If you're lucky enough to get into alpha testing, then you're one of the few that get to test the end game content with high-level characters throughout the beta. That's how most games work. They want the most dedicated testers, the ones who give thorough and drawn out feedback, to test their end-game throughout the whole developing process. During the end of closed betas phases, they start giving out more keys in order to better stress test their servers, and then open beta further stresses the servers out.
At least that's how most well-known devs do it.
All-in-all the game is great. Lots of graphical glitches, broken quests and major lag spikes, but other than that the game is pretty polished for a closed beta.
EDIT: Remember, beta tests are not to play the game as if it's launched. It's to test for bugs and shit, especially in the early levels.