Red Mage and Dark Knight for me. Though they are my second choice. Rogue and Ninja was my first choice so I'm excited to see them come in the next major update.

As for the topic of thieves. I don't get why everyone is in a tizzle about them not being called thieves. In D&D they used to be called Thieves until 3.0ed. But I can see why it was changed in D&D and the same reason is being used here:

All Thieves are Rogues. Not all Rogues are Thieves. So you'll be able to do your thiefy thing and dress like a thief with thief weapons as a Rogue and you could even RP as a thief if you wished. But the good news is, anyone wishing to Rp their Rogue as Not a thief could reasonably do so. Thieves are thieves because they commit thievery. But what if you have all the combat capabilities of a thief yet never steal? You are a Rogue in that case. Perhaps you spy, kill, or troubleshoot instead.

Basically the only difference is in the UI will say ROG instead of THF or THI or whatever Thief would have been. Not to mention people coming from previous MMORPGs will instantly recognize the Rogue and what its capabilities will be.