A "decked out" rogue would not have 350 HP. Too low. I had my Bard at level 20 for like, a week, and he had more HP than that. I'm sure a Rogue can manage to find a way to beat my silly Spellsinger.
And said rogue wouldn't get creamed by a DBF, or Chain Lightning. Nor would the Monk, or the Ranger.
If you didn't want a sign up list, why even pop this up on the forums? If their toons are on timer now, they'll (very likely) still be on timer 4-6 hours from now. If you really wanted to afford people a proper "heads up", shoulda done it 60~70 hours ago.
Still don't know which toon's 20th this is for you. Maybe you don't know who the other 11 people in your party are going to be, but you could at least let them know what you're bringing to the festivities. Seems like a fairly simple courtesy.